I have my FP4 since release and I miss A12. So I thought about using a custom ROM.
I would like to have google Services, so I thought about LineageOS. Are there some other custom ROMs that have A12 (maybe soon A13)?
An other question is, do I void my extendet garanty when I install a custom ROM? Or do I just don’t get support while I have the custom ROM installed? And is there a way to get the phone back to Stock (unroot and FPOS with google services)?
You cannot use the warranty if you install an alternate OS, you will have to reinstall the original to use it. In doing so you will loose all data if not backed up and you may have problems resinstalling.
It is best you just readup on all the OSes that are available, there’s no short answer.
Read up on warranty too
Search this site for each OS you are interested in . . .