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.