Updates on the issues from post 1
As suggested by @piero , installing an alternative launcher (I tried Lawnchair and Kvaesitso as both are FOSS - both recommended) solved issue #1 : removing persistent icons at the bottom of the home screen. I now know :
- That that space at the bottom of the screen is called the Dock
- How to get notification access to work - Lawnchair FAQ
It also solved issue #2 : placing icons where I want on the home screen : Lawnchair allows me to place icons wherever I want on the homescreen, and Kvaesitso doesn’t allow me to place any - removing the issue.
Intermittent luck with issue #3 : shortcuts on lock screen. I have been able to get them sometimes, but not always, and only using Kvaesitso. I guess it’s a question of enabling the right permissions for each launcher, 
.
Success with issue #4 : Pressing the power button twice on lock screen now starts the camera while locked. I think enabling notification access fixed it, but I’m not 100% sure. If not, try looking at app permissions, and unticking “Pause app activity if unused”.
#5 : Back navigation button often closes the app instead of navigating to previous page seems to also have gone away, although I can’t say with 100% certainty. If this does indeed not revert, I would again assume it’s related to launchers and permissions.
#6 : Up time: only gives hh:mm:ss, no days. Well, now it gives hhh:mm:ss, which I guess is an improvement as you just need to divide by 24 to figure out how many days that makes.
#7 Didn’t require more digging.
#8 No news.
#9 : Work Profile tab at bottom isn’t visible was also solved by changing launcher.
#10 - 13 : No news
I hope this is useful to someone going through the same issues!
– o1vpr –