On the M1-
Madmapper does a great job of decoding HAP codecs.
You can encode to HAP on an M1 using FFMPEG in terminal or AfterCodecs in Adobe Media Encoder / After Effects / Premiere.
You can not decode HAP very well in any Adobe program, so if you're given a big old HAP file and you need to quickly adjust something, there doesn't seem to be a good way to do this on a Mac right now. I've tried to decode from HAP using FFMPEG and it hasn't done very well.
Best thing I've found so far is to use Syphon recorder out of MadMapper but the timecode won't always match up
Any other ideas out there?