So, I was searching this up but i only got results for skills, is there a way to use it as a controller for anything else?
Yes you can.
How would I set up the brain?
Read the linked page, follow the link to install the field control program and install it.
Isn’t it a one way operation that was described in the linked thread and cannot be undone?
I guess, the only meaningful explanation why Event Firmware could not be uninstalled may have to do with the price of the regular V5 Robot Brain (currently $363) vs the price of the Smart Field Controller (currently $155 (subsidized?)), which from the hardware standpoint appear to be identical.
Because, if it was only a question of ensuring integrity of the trusted Smart Fields Controller operation, then you could have Smart Field Control option to be present inside firmware of every standard V5 Robot Brain.
You can run the field control program on a normal brain, no issues.
If you install the field controller vexos on a normal brain that cannot be reversed, but you need to try really hard and mess with the tools to be able to do that.