So it’s hard on some phones. Lineage OS support also isn’t any indication of how hard it is to unlock. The more popular devices are all easy to unlock.

That’s just confirming it’s generally extremely simple.

Which would help how? If they are really going to make it much more difficult for custom roms it doesn’t matter what phone you choose.

I’ve used nodm for something similar. I used to show my homeassistant dashboard on it using a kiosk session in chromium in a nodm session. It does require some fiddling, but it does the job perfectly.

For games you could also add them to Steam and use proton if the game is supported, but lutris should be pretty straight forward, it was for me anyway, in Ubuntu.

Still, Linux can be a challenge in terms of non supported games.

Security is definitely a concern, so replacing it is recommended. I’m not sure about other browsers compatible with Chrome extensions though.