Now, the confusion starts.

- is it enough to connect the HC just once for a certain location to sync the GPS data?
- or I need to do this every session?
- is it save to disconnect the HC after GPS sync and proceed with Ekos?
- my concern is the Meridian Flip - if the HC is connected it will interfere with Ekos.

What is the workflow? Anyone?

OK.
Looks like I figured this mount out.
I am testing it outside for guiding right now.

Performed the PA routine. It worked nicely.
Control knobs of the mount are very smooth.

Guiding is good at around 1" RMS total (0.5 sec interval) with occasional RA runaways.
I had to adjust Min/Max parameters quite a bit (from what I am used to with HEQ5) for guiding to work.
Internal guider.

Can someone please share good Control Parameters for the Internal Guider?
Will be much appreciated!

Running it outside with everything attached.
Will have the flip in 15 min.

Guiding is good - below 1" RMS but even after tweaking I still have RA runaways every 1-3 minutes.
Those are just spikes which settle in 10-30 sec.
I guess it's OK but if someone knows how to get rid of them - please let me know.

For guiding I settled at:
Min/Max RA 120/12
Min/Max DEC 1000/12
0.5s guiding interval.
Internal guider.

Thanks!

The flip didn't go well.
It went under horizon.
When I parked after that - the position was off by 90dgrs in RA.
I guess, I had to have "simulate pier side" option enabled (without it the pier side was "unknown').
Next time I'll see if it helps.

Also, after the flip, the DEC guiding became worse (still good at around 1") but RA spikes disappeared.

Continuing talking to myself...
Tonight, I am having the second night out with the mount.
Same thing - guides smoothly at 0.6-1.0" RMS total and then every 1-3 min RA spikes.

Out of curiosity I installed a counterweight (2kg). Luckily, I had a proper shaft and a weight.
Guess what? No more RA spikes/runaways!

That's with my smallish AT72.

I wanted to lighten my travel bag with this mount but it's not going to happen, I am afraid....
Guiding is really great at 0.6-0.8" RMS total now.

Did you sort out the flip? Was it side of pier? I haven’t used mine with StellarMate/EKOS in a few months. Been using ASIAir and trying NINA. But previously had no issues with the meridian flip. I did have to set a 5° past meridian limit in the hand control, then set EKOS to flip at 3 minutes past meridian. That seemed to work for me. I’m anxious to get back to EKOS, as it’s still my favorite capture application. But we’ve had such a string of bad weather, it feels like it’s been a month or more without any opportunities to use it.

Yes. I don't know what happened the first time I tried the meridian flip...
The second time it worked fine.
Also when I enabled the "simulate the pier side" option it made matters worse. I keep it OFF.

The pier side is "undefined".

I don't use the hand controller at all.
I figured that it's only needed to be used once to push coordinates/date/time to the mount for a particular location.
If you travel to a different location/time then the HC needs to be connected again and synced with the mount.

So, my scope is in the default RST Park position (horizontal, facing west).
I connect to INDI/Ekos and there I have its Park position defined as facing NCP. So, I park it from Ekos and it goes to NCP.
In the end of a session I manually drive the mount back to horizontal position (with Ekos Mount Control).

I sometimes encounter problems where the mount travels the opposite direction of where it's been asked to go. For this reason, I home the mount every single time I boot it up. I've also seen where I might start it up, home it, and let it sit for a few hours, then issue a GOTO command and it doesn't know where it's pointing. So I have to home again, then reissue the command. I have no idea what causes this erratic behavior. I've also seen on occasion that if the mount moves from west to east, and you send it back west again, sometimes it thinks the shortest route is to continue east until it gets back to the point you sent it to. This makes the cables wrap around the mount. I also don't know why it does this.

But typically homing before using the mount in anyway keeps all these scenarios from happening.

Yes, I think it's a good idea to have the HC handy in case the mount gets confused.
I intend to use this mount mostly for travelling to dark sites - I will need it anyway to update the location.

I found that leaving the mound in the "standard" parking position - scope pointing at NCP is pretty safe in terms of the backdrive.
So, in the end of a session I don't bother anymore driving it to RST's default home position (horizontal facing West).
Just reporting.

Waiting for the good weather to return and the Moon to go away to play more.

Update...

-- good people here on INDI forum recently fixed the driver (thanks!). Location push is now behaves as it should. It's only available on beta channel at the moment.
-- I went out to a remote dark location with RST-135 and RC6.
-- had the hand controller connected and GPS signal acquired.
-- launched KStars/Ekos (KStars was set to Mount updates KStars). Location got updated nicely.
-- all was good but I didn't realize that I had to change my parking position (pointing to NCP) - it was still using my usual location/longitude.
This caused some issues since it was parking in a crooked way. Once I copied/pasted the new longitude to the parking position everything became OK.

-- new thing I didn't know before - if you click Home Mount in INDI control panel RST-135/Main Control this will home the mount as the hand controller would (horizontal facing West)