Android is open source, it’s literally in the name (AOSP-Android Open Source Project). As long as you can unlock the bootloader, you can flash whatever you want. The problem is relocking it, unless you have a custom AVB key, you can’t and I believe only pixels can be relocked with a modified boot image/OS, and nobody wants to limit themselves to one brand. The problem is Google got rid of the dedicated recovery partition and moved it to the boot image which makes flashing on the go damn near impossible because you have to be tethered and use fastboot commands. Graphene does have OTAs, but, fuck that noise. Not to mention all of the big names that used to bring up the new OS’(mainly Alex Cruz and team DU and Martin Coulon from GZR) are retired or passed on and no one else knows how to do it so they just copy/paste whatever is available, which usually leads to issues because they have no clue WTF they’re doing. Is Kdragon still around? I have been #teamapple for a few years now, it’s the best decision I have ever made. Sure, there are some cons but, at least for me, the pros far outweigh them. I suppose you could jailbreak it but that defeats the purpose of buying an iPhone.