Can I power nodemcu v3 with 12v?

Just wondering if it's possible.
I have the nodemcu v3 lolin

Possible.

But not a good idea (if you power anything but the NodeMCU itself your regulator will overheat - that includes the blue built-in LED).

I wasn’t ever able to get it working reliably at 12v...

I would not try to run something that pulls as much current as an ESP32 can from 12v via a linear regulator. Use a buck converter to knock it down to 5v (these are readily available, often with USB port output for power), or all the way to 3.3v and power via 3.3v rail.