pinephone pro - is defintely getting better as the software improves. The battery life is definitely something that holds it back i bought a keyboard battery case and it improved it however the edges of the case that connects to the phone have cracked over time and ive super glued it twice (near headphone port & opposite side near type c port.) When they crack it can cause a misalignment on the pins and not charge/keyboard doesnt function so i have to press back into the case(hence the glue to fix that). It will eventually get better for me to completely jump over.
Pixel phones degoogled - works great especially calyx or graphene os. I have always bought used but if i want change to happen i need to stop funding google indirectly through the used market with buying their phones. I am speaking for myself here.
Fairphone , Teracube, Murena - i eventually want to just buy from these moving forward. They hit 80% + of the checkboxes i need and improvements come quicker when this companys market improves especially when their direction aligns with what i want in a phone.
Tl;dr - i am letting my money do the talking on where i want phone improvement to occur.
Regarding best phone for post market os
https://wiki.postmarketos.org/wiki/Devices
Pinephone (not pro) seems to have the most support its on the main line.
Other than that under "community" & "phone" you would decide which phone in that list meets what you need and get peoples opinion on those specific phone with usage.
If you dont mind tinkering go pinephone however if you need it to work for various uses based on what you/friends/family use and compromises need to be done then go android.
Contribution can be bug reports, donations, assistance to other users ect. Anything is possible if you want.
I do where i can and its my choice; same with you, your choices are your own.