1.5.0 seems to be the best SM release for RPI4 so far.
WiFi hotspot is finally working reliably (I don't really need it anymore but still it's a big improvement).
Only tried things indoors. Everything seems to be OK.
Tomorrow night will try outside.

A couple of questions:
-- What about the updates? How to install the nightlies?
-- How do I prevent KStars from starting automatically (in Ubuntu it was easy...)

Thanks!

Dashboard updates never end

In my usual 'Do it yourself, damn the torpedoes' mentality, I tried to create my own Raspbian based system from sources only. Happy to report that I got everything installed, KStars, Indi drivers, everything showing up nicely, although I also encountered problems with the dependencies as shown in an earlier post here, which I solved, by installing them one by one.
At that point, I thought it was appropriate to open the champagne and have a good sip.
Glad that I did, because when I tried to use it with my equipment I got a KStars crash. Intriguingly, every single one of my components registers and starts fine from Ekos and/or the Device Manager, but for some reason when I want to start my Polemaster together with the ZWO guide and image cameras in Ekos, Kstars crashes. Same happens when I try to connect to a camera and to my iOptron SmartEQ mount at the same time, i.e. during Ekos startup.
Has anyone seen that kind of behavior? Clearly, the driver are there and working, but they do not like to work together.

The same system constellation is working just fine using Ubuntu MATE as the OS, so it should not be an inherent driver or KStars problem. Must have to do with the way I installed it on Buster.
Does anyone have any ideas what the mistake could have been?

El Corazon - see if any of your devices have 8bit / 16bit drivers and try the 8bit settings. I had to do this with the ASI120mm mini, not sure if that is the same as your 120mm-S.

When I first used it, I had screen tearing issues with noVNC (I think that's the term), but Jasem on another occasion told me to clear my cache in my browser. I did that and it cleared right up!

I also didn't like the screen colors and odd fonts (to bright), but that was easily changed with Raspbian screen preferences.

And in order to get the new Sextrator astrometry feature you need to run the following: sudo apt update && sudo apt-get upgrade -y && sudo apt-get dist-upgrade
Here is the discussion of what it is:
knro.blogspot.com/2020/02/kstars-v340-is...kdhoXFcTYE59Xt8yFbiQ

Oh yeah, make sure your ZWO camera is taking 16bit images instead of 8bit. Not sure this is a new release issue (I seem to remember my last night with the old version did this). But just check. Change it in the INDI camera setup section.
"wvreeven wrote: Start Ekos with the cameras attached and go to the last tab in the configuration editor. There at the bottom you can set the bit depth. You may want to override the *.default config files in the .indi directory in your home dir with the lastly saved ones so this won’t happen anymore."

@Max: A couple of questions:
-- What about the updates? How to install the nightlies?
-- How do I prevent KStars from starting automatically (in Ubuntu it was easy...)

@megiddo: And in order to get the new Sextractor....

I want to second Max's questions.....I've not seen any updates yet (seems suspicious...there's usually some updates by now). I also want to know how to disable KStars from autostart. Finally, it's not clear that to use SExtractor on SM OS 1.5 we need to do the sudo apt commands. Can someone confirm this is for SM OS, or is this just for DIY installs?

For the Sextractor (Sex Tractor What??? ) Update... I opened a terminal and entered (copy & paste, using the noVNC clipboard icon, very helpful)

sudo apt update && sudo apt-get upgrade -y && sudo apt-get dist-upgrade

On the copy/Paste in noVNC, click the clipboard icon, paste in your item.... select it all again and copy it. Seems to be the way that works for me. You can also do the opposite from the SM back into Windows.

This thread is for Stellarmate 1.5.0 Users, not people have built there own raspbian based system, so your best to post in the general Kstars section....

The 1.5.0 build posted on stellarmate.com 3-4 days ago SexTractor is preinstalled.
Initial/older build didn't have SexTractor preinstalled.

Answering my own question.
Jasem said that the updates should be done via StellarMate Dashboard.
Currently there are no updates.
Will be soon.

Overall it is working well. Using KStars 3.4.0 with Stellarmate 1.5.0 on RPi4. I do have an issue on startup. Every time I restart Stellarmate and then connect via EKOS, the first time I hit start it fails to connect. After that it connects fine until another restart . If I connect via VNC I see the same behavior; the connection is rejected the first time, after that it connects fine.