I have tried 6.6.x a couple of times now when rc and now its stable and am getting random hangs. Using 6.5.x have had no problems after downgrading back to keep the family happy. Even had 60 day uptime on 6.5.x
Ryzen 1700
32GB hyperx
ROG hero motherboard
These lockups seem to happen mainly when system is not under load and over night.