Hi!
My friend is looking for an Android tablet that has an unlockable bootloader and also has a custom ROM. I’ve checked a lot and every one of them is problematic. Usual brands here are Samsung, Lenovo, Huawei, Honor, TCL, Xiaomi. Apparently Huawei and Honor is out of question since they don’t allow unlocking bootloader. TCL is new so no ROMs. Xiaomi seems possible but unlocking a Xiaomi device recently became even more pain.
Do you know a decent model from these brands? Preferably 10-12 inch screen.
if you go for an Android tablet go for a Wifi only model, mobile network devices are usually not supported by custom roms. Anyway I would also suggest to look at Linux tablets, no tinkering with locked bootloaders and bricked devices.