I'm curious why you can't legally pay in crypto? I heard a few times about companies paying in crypto to their remote workers. In fact I heard that a US company was paying in BTC withing the US, though I'm not sure I trust this particular story. I also see that Deel accepts USDC, and to my understanding they convert to local currency of the remote worker. Is that all illegal? Truly want to understand.

It's probably legal as long as you do all the same accounting/withholding that you would normally do. I suspect some companies are forgetting to do that, just as many people forget to report taxes on crypto.