IMHO, that sounds a little bit confusing. There is a very nice ROM, obtained from the new motherboard (so, it is not Russian, it was just available for download on Russian forum). And there is an official OTA upgrade for that ROM. Everything is working perfectly, except fingerprint scanner buzzing ...

It is an official ROM update via OTA. Trust it, nothing to fear ;) and please remember to perform a factory reset after each update to avoid weird issues. I have updated to android 8 trought "Local update" and since that time there is a lot of bug. Can I expect a notification for that new...

this isn't the android 8 subforum, but the old 7.0 which is/was more stable

When I start android auto on my phone without being connected via USB or bluetooth, they remain, only when I'm connected via USB they dissapear after I disconnect.
I've got a brand-new volkswagen.

I found the reason: after connecting my phone to my car and using android auto (via USB) they dissapeared after I disconnected.

after I lost them yesterday again, I didn't charge my phone this night and they remained, so maybe that has something to do with it?

I lost them again without even rebooting, I only recharged my phone this night

I can't even remember since it's been so long ago, I haven't even installed or removed any apps in weeks

same here, with the last official 7.0 build that's been made available via OTA without rooting

don't hold your breath, unless support is build in on a future stock android, chances are you'll never be able to have descent universal VoLTE support but will always have to hope for provider-roms and they hardly ever make them for other models than what they sell you themselves