i have a serrano hot pepper l55b phone purportedly with a unisoc chipset, running android 10 based on treble. these phones can be gotten very cheaply, with a free plan, in the usa. although i think the phone you get from the program changes. i got mine because i got on foodstamps, at my family's request, and i wasn't set up with a working phone, and this worked out for me. it would be a good thing to make the phone run a custom rom so all the other people who use it could use a normal phone. it is not normal when bought. it is full of advertisements, very slow, and it wouldn't let me use it to tether. i think it has other limitations too. i searched earlier for OEM unlocking on the phone, but did not find it. now, with my experience just working on the unihertz titan, i found OEM unlocking. it is under system->advanced->developer options. although somebody told me this phone could not run a gsi, it looks pretty likely to me that it can. if the bootloader can be unlocked, and there is a public factory flasher, then we just need to put an appropriate treble system partition on it, and it might run like a thousand dollar phone from silicon valley, dunno