So after 3 month of my sufferings, my final decision is to run away from Nokia.
My Nokia 6 TA-1021 was excellent on Android 7.
I'm even joined beta test and reported about some bad issues... But..
In short, about my experience. After update to Android 8.
btw i'm reading this forum, i know much about tricky things, that can be helpful in repairing my issues. All that issues are already discussed here. And i tried to fully reset my phone.
1. Cracky sounds, tried everything, but no luck.
2. Strange line flickering on screen sometimes.
3. Apps still keeps closing with everything energysaving for them are turned off.
4. UI in Android 8 are much less responsive than in Android 7 with some strange freezes for a moments.
5. Online FM apps on Car Bluetooth stops to play after 1-10 minutes of playing.
6. Unblocking screen with keyprint sometimes make screen split.
7. Native Camera app shots with yellow tones and with excellently poor quality.
8. Watching any videos in browser are laggy. Sound are fine.
9. On low volume can hear a silence, then some distorted sound.
10. Android 8 stopped working with my Android Pay. All time "You moved out device too fast, try again" or "Error, try again"
11. When trying to answer a incoming call, sometimes screen begin to jump up and down until i press On button twice.
12. Sometimes answering a call can be a very tricky, because a button "Answer" trying to hide, in first it hides on screen and it need to open top menu, where i should find a row with call, move it down with a finger and press "answer" then.
Not a full list of issues, but i'm very unpleased that i see no patches from Nokia, only security updates.
Thanks much for that excellent phone and shame on you for untested Android 8. Thats enough.
So, i downgraded to 7.1.1 and then updated to 7.1.2 and turned off updates in developer menu.
And now all described problems above gone away.
btw. All issues gone. And problems with randow cracking in calls also gone away, before i my thinkings that is because of network operator.