I pushed a possible fix to master, please check.

Hi Max,
Sorry, that it another week passed by.
Did you try building from my fork or any of the test builds, that astrophy created?
I need to still make it compatible for the normal lx200 users and will be working on that soon.

Grimaldi

Sorry, I am not advanced enough... I can only use whatever updates are available in Stellarmate..

I got some news. Sorry for the weird form I'm posting this:

1. I built Jasem's latest master commit "a59f2f570465ce28c535770d451e334b4fb661db"
2. indi_asi_ccd seems to be broken
   • it crashes immediately after connecting the devices/drivers
   • might be a problem on my side since I only built "indi" and NOT 3rd party drivers, where this might be included
3. Location gets received from RST-135 to Ekos kind of...
   • kind of=
     • The problem which is described some posts above is still present. Ekos overwrites any set location in RST-135's EEPROM even if "Mount updates Kstars" is selected in settings. I found a weird behaviour though:
       • It only get's overwritten when Ekos/INDI Server is started from scratch out of Ekos GUI via the play button
       • It does not get overwritten when only the devices/drivers are disconnected and reconnected
     • I saved test coordinates in one of RST-135's location slots: E22°22'22" and N22°22'22". When this data get's received by Ekos it only receives 22:22:00.0 and 22:22:00.0. It seems to loose arcsec resolution.
4. Date & time are still not received properly by Ekos
   • Error message in Log: "2021-06-02T20:03:36: [WARNING] Could not process mount date and time: :GC06/02/21T00:00:00"
     • so it does not ignore ":GC"
     • and it does not receive time

Hope this helps in any error finding & I'm sorry that I cannot help more with programming myself. I maybe could to it, but this would take ages.

I could not let it go. I have a working indi fork now on my git:  github.com/jimmy-ck/indi
It took me a lot of commits since I had to share and debug between my Mac for programming and my RPi for building and testing. First time I'm using git, so maybe this could have been handled better. 

• fixed:
  • location accuracy is now received in arcsec resolution
  • date & time & UTC offset are received properly now
  • it should not interfere in any ways with classic LX200 mounts
  • I renamed a lot of "title" comments because I found them misleading
• not fixed:
  • indi_asi_ccd issue mentioned above (which maybe is not a bug)
  • location in mount gets overwritten when Ekos is started from scratch

Question to Grimaldi and Jasem: How can I do a pull request to indilib master?
Found it out myself: Pull request #1478  github.com/indilib/indi/pull/1478

If you‘re open to a new editor, you can install Visual Studio Code on your Mac, install the Remote extension and then have connect it to your RPi. That‘s how I do it.

Astrophy did a good job, AFAICT. And as I neither have a RST-135, nor a lx200, I feel it's better, if you collaborate on fixing it. Thanks for your patience.

@Grimaldi: Thank you for your help as well and pointing out Visual Studio Code remote – that works way better for me now.

I created a new pull request  github.com/indilib/indi/pull/1481 , which should fix everything inside of rainbow.cpp without touching lx200driver.cpp.

The only open thing now seems to be the location override of the mounts by KStars when starting Ekos from scratch. As far as I understand the code this must be a general problem which should affect ALL mounts though.
My current workarorund:

1. Start KStars
2. Start Ekos/INDI and loading drivers/devices
3. Using RST's hand controller to store GPS data into mounts location slot (by long pushing ENT in GPS menu)
4. Disconnect drivers/devices in Ekos
5. Reconnect drivers/devices in Ekos >> now Site Management Tab of RST-135 shows the correct location in INDI Control Panel

Thank you, guys, again for working on this!
I wish I could test the fixes...

By the way, as far as I know Rainbow released a new ASCOM driver not long ago.
Maybe that could be of some help?

I created  github.com/indilib/indi/issues/1484  regarding the location override on Ekos start with logs attached.

@Max: I don't now how Stellarmate updates are rolled out. Jasem merged the fix into master branch of INDI yesterday, but I think the builds are not included yet in nightly. As a quick solution you could backup your /usr/bin/indi_rainbow_telecope by renaming it with "_backup" attached and replace it with the attached binary, which includes the fix (built for Raspberry Pi 4, 8 GB). No guarantee though that this works by just replacing one binary file (I had to manually rebuild all 3rd party drivers to get it running).
 

StellarMate beta channel should have the updated drivers since they're updated daily.

Great - will test tonight!