The system requirements of 19 state this: “Note: on an M1 mac it is NOT supported natively yet. You can run via Rosetta and therefore the performance won't be as good as it will be once native support is added.”

I guess we can interpret this that native support is being worked on.

Been using H19 on my new Mac M1 Max for a week now. Seems to work quite good in general. Have big issues when trying out "stage" but since I don't regularly use it I can't say if it is a M1 Max issue or something more general. (it seems to loose viewport focus all the time and it only comes back if I switch to another app and back again).
Regarding plugins I have tested Redshift and VRAY with seems to work ok as well using the latest releases (nightlies in the case of VRAY).
The coolest part is H19 has support for EDR in viewports with means I get full HDR insanity when things normally would have been blown out. Shades on!