Ok, lots and lots of reasons for a techie not to move to HK right now, and OP hasn't given any reason why they specifically want to, or what they'd bring that would make them employable...
So let's go back to the original question(s) - how easy will it be for an American software engineer to get a visa right now, and how likely is that to be an obstacle to hiring?
For the first one, if you can get a job offer from an established company, particularly one which already employs people on work visas, it shouldn't be a big issue. For a tiny startup, it might be more of a problem, and it does seem that Immigration, apart from just being busy/slow, are also being stricter on requirements for things like proving the company tried and failed to hire a local before going abroad.
For the second one... a lot of the stuff above still applies - hiring is depressed generally, the market is turning more to a China focus, hiring/visa/quarantine is slow - so you're putting yourself at a massive disadvantage compared with people who are already here and locals. Unless - I know I sound like a broken record - you're bringing something special, it's not going to be easy to find something from abroad right now. Not impossible, but hard.