Island, Insular, shelter all use Android for Work. There are other options like Private Space.
They give some isolation, but I don’t know how much it helps.

Do Insular and silimiar apps block app from scanning?

Unlocking phones has more to do with the phone’s manufacturer than the SoC it uses. Developing custom ROMs for MediaTek is more difficult. However, that doesn’t mean there aren’t devices with MediaTek SoCs that have custom ROMs.

Unlocking is possible outside of China https://github.com/melontini/bootloader-unlock-wall-of-shame/blob/main/brands/xiaomi/README.md

There aren’t many good options for Linux phone… https://linmob.net/resources/#smartphones

I need to wait. Custom roms development for my new phone has only just started. Right now, there are only beta releases of LineageOS (unofficial). It doesn’t look that bad even though it has a MediaTek SoC.

I will move to custom roms. There is no way I will don’t use revanced.