On which reasonably modern/performant phones can one install them? I did bought an iphone as my latest phone, because Google-riddled android is ridiculous (even though I like the ecosystem much better. Iphones can feel like some embedded software that only allows a few possibilities), but mainly because I could not find a phone on which installing some AOSP fork is safe, won’t delete important firmware (I believe quite a few mobiles will delete proprietary camera firmware)

It's mainly on Pixel phones, ironically. Has something to do with the security chip they come with