BEFORE doing anything else with that machine, please read. I wrote several guides about Umbrel and LN nodes, here is a dedicated section.

And here you have a special Getting started with Umbrel

Please don't jump into something that you do not understand what are you doing. Read first, before doing crazy stuff. Is very important not just for you, but for everybody. Why? Because LN is a living thing. You screw it, you screw the rest too.

How much is a Pi4 where you live? It's around $100 here in India