Hello,

Ideed, this is possible.
I bet the built in Wifi does exactly the same thing that the SkyWatcher wifi dongle do. My dobsonian goto mount does not have built in wifi, but I have the dongle.
So what the dongle does is it connects the motor controller serial port to an UDP socket through the wifi. This means it is the low level motor controller protocol that goes in that USB socket. You can connect to this UDP port using the SynScan app on your phone or windows desktop.
The synscan app also provides an UDP port, a differtent one (even different port number), to which you can connect with an other program, like skySafari or windows ASCOM driver. It is the high level SynScan protocol that is going in that UDP socket, the same that goes on the handcontroller serial port in the traditional way.

In theory you can connect to the Synscan app UDP port using the indi_synscan_telescope driver through the wifi (there may be technical dificulties and driver bugs, but it can work)
Also you can connect to the built in Wifi/dongle UDP port using the low level indi drivers: indi_skywatcherAltAzMount and indi_skywatcherAltAzSimple driver. This does work for me. I'm atively working on improving the driver in this sense.

Regarding the serial ports: There are two quasi standard for serial ports, as you may know. The one is commonly calles TTL, although nowadays it is more like LVCMOS 3.3V not the old fashioned TTL +5V level. But most of the so called TTL serial cabels can tolerate both +5V and +3.3V levels.
The other is the classic RS232 levels: +/-12V. That is not directly compatible with the TTL cabels, neither vica versa. So you need a standard USB-RS232 converter cable to connect to this type of ports. These tipically ends in a standard DB9 type connector. That is how you can tell it by just looking. The TTL cables almost never ends in the DB9 (old fashioned serial port) connector.
The conversion between the two levels is rather easy, only one chip (so called MAX232) is needed. It is also common, and standard so I'm sure it is also available in the US, there is nothing for the the FCC to regulate here. Most o the USB-RS232 converters works internally by using an USB-TTL-serial chip and a MAX232 (or chines clone) chip.

The motor controller typically has TTL-serial on the connector, while the hand controller has RS232 or direct USB to connect to the PC.

The handcontroller also has a so called "Direct-PC" mode, in which mode it directly copies the traffic from it's serial port to the motor controller port (and vica versa), so in this mode you can connect the hand controller serial port to the indi driver (the low level ones), and use effectively the hand controller as an expensive TTL-RS232 level converter. This mode mainly used for upgrading the firmware on the motor controller from the PC.
Of course maybe your hand controller is different from mine, I don't know.

I have checked:

- The SkyWatcher WiFi dongle listens for connections on UDP port 11880

- Unfortunately indi_skywatcherAltAzMount and indi_skywatcherAltAzSimple driver does not connect through UDP, it seems that the code in SkywatcherAPI.cpp does not properly handle UDP connections (it tries to read byte by byte from the socket, which does not work. It is either incomplete or broken).

- The synscan App listens on TCP port 11882, and the indi_synscan_telescope driver can connect through WiFi and TCP. The important thing here: I was wrong, it is TCP not UDP!

I mentioned this before, but any luck with EQMod or AZ-Gti drivers?

I bet the eq_mod driver can only work in equatorial mode, isn't it?
The AZ-Gti mount can be put on an equatorial wedge, but it is not an option for a 10" dobsonian telescope, or like.
Some time ago I made an experiment with my Virtuoso mount, I've put it on a Photo legs in equatorial position.It has worked with the eq_mod driver (through Wifi and UDP), bu as it is impossible to balance that mount in that config, it is not a usable solution for me.

I can confirm that the new SynScan built-in WiFi also uses UDP 11880.

As I have said, I have good results with Kstars/EKos/Indi talking to the indiserver indi_synscan_telescope over WiFi which talks to the SynScan APP on an andriod tablet that controls the mount via WiFi. I just want to lose the tablet, as it seems to just pass data. After setting up the connectivity, I never touch it.

No, unfortunatelly the tablet not "just pass data". It is the synscan app that actually controls the mount, tracks targets.
The indi_sysnscan_telescope driver sends commands to the synscan app like: "goto this coordinates", "track at these coordinates". The synscan app control the mounts with commands like "roll motor for AYIS1 at rate ..., roll motor for AXIS2 at rate ..." and does that periodically. Also the driver ask periodically (about once a second) the synscan app about the status of the mount, which reports what celestial coordinates it is pointing at. The Synscan app reports the coordinates in RA/Dec coordinates even for an Alt/Az mount (also reports the ALt/Az coordinates, which sometimes causes confusion in KStars).
So in this setup you cannot just lose the tablet (you can replace it with a Windows app, but that cannot run on the RPI, so it is not easier in any way). Yes, sure, you must touch it only for setting up, and alignment. Later it is pretty much working by itself, but the synscan app is the one that does the hasrd wortk.

To lose the tablet you need to use an other indi driver, which is capable to directly communicate with the motor controller, and do the hard work of tracking. This can be the indi_eqmod driver or one of the indi_skywatcherAltAz drivers.
The indi_eqmod driver is for equatorial mounts, as far as I know. It is capable to communicate with the via UDP. It is unable to communicate to my Virtuoso mount via serial cable due to the way the serial port is built in the Virtuoso mount. Other mounts may work.
The indi_skywatcherAltAz drivers use a new common SkywatcherAPI "library" within indi, which is pretty promising, but at the moment does not work via UDP, only direct serial cable works. There is no theoretical reason for that, there is hope that it can be fixed at some time in the future.
These indi_skywatcherAltAz has some annoying bugs/misbehaviors that makes the inid_synscan driver more suitable for eye observations (for example: the joystic control does not work), but at least the indi_skywatcherAltAzMount works pretty well with camera and plate solving.
The indi_skywatcherAltAzSimple driver is a bit too simple to my taste. Instead of continuous tracking it makes small gotos every half a second or so, which makes the whole scope shaking a bit. It is OK for shot focal length (DSLR on a skytracker) but not good enough for a 1000mm focal length scope.

Thank you for that reply. That was information I didn't have and had been looking for, hence my misconception regarding the SynScan APP's role. You have given me hope, however. I can see using the indi_skywatcherAltAzMount driver with a cable, once the serial-to-mount-dongle released in the US. In a worst case scenerio, I was once a fair network programmer. It has been a decade since I wrote any code, but there was I time I could hold my own in Java, Perl or Assembler in large architecture global networking processes. If I get very frustrated, I might possibly dust of the cobwebs and attack the problem. I might still be able to sort out a single point-to-point UDP issue.

If you are an ex programmer than an alternative is to use an ESP32/Ardunio sketch to enable serial to UDP convertion (just plug in the ESP32(usb version) creates a serial port and the coding in the ESP32 can pick up the serial data and do transparant convertion to UDP (and visa versa). It works but ESP Wifi signal isn't the strongest IMO - but it works. If you google something like " transparanet serial to UDP arduino " there is a basic sketch out there but it does need mods to enable it to work with SW UDP (mainly port numbers!)

Here's your starter github.com/roboremo/ESP8266-WiFi-UART-Bridge :-)

Just a thought

Hmmm. I already have a Pi4 on the scope running indiserver, it would make sense to make use of that WiFi....but I do have an Arduino that I used for a stand-alone WiFi focuser using Java and python when I got the scope. Funny thing, one of the first commercial programs I wrote back in 1978 was a transmission program for the 8250 UART for use in terminal modem programs. Things have a way of circling back around. Perhaps it is time to dust things off. Thank you for the link. I'll take a look.

You have said that your mount already have the wifi dongle built in, isn't it?
What kind of mount is that?

Here is a picture of the HandUnit (that I no longer use) and the ALT motor) on my SkyWatcher 10" Dobsonian GOTO. The three ports on the HandUnit are: Connection to Motors (left, curly cord), Camera Control Port (center) and USB I/O. Note the WiFi symbol on the motor. I am not sure if the WiFi device is in the ALT or AZ motor, but I suspect the ALT motor, as it has the power connectivity and other ports.

I have recently found documentation for the Camera Control Port and believe it may =possibly= be a direct serial input to the motors. The pinout is:
1 - Shutter
2 - TX (RS232C)
3 - Ground
4 - Common
5- RX (RS232C)
6 Vpp+
It may be that wiring a USB cable with pins 2, 3, 4 & 5 properly connected to a RJ12 plug will be the means of communicating from the Pi to the motors. I know that the Telescope Mount Port is TTL, so that's not an option without hardware. Connecting through the SynScan HandUnit USB port is the same as WiFi through SynScan APP.

RATS!

No...I'm wrong. That's the port on the EVIL HandUnit. No point in messing with that... may as well just us a USB cable plugged into the HandUnit USB port. And it would be back to the HandUnit requirement. Sorry for the misdirection, but at least you can see the mount setup and built-in WiFi.