My mid-2012 13" MBP (which essentially has identical innards to your Mac mini; Ivy Bridge chipset etc.) has been exhibiting the exact same behaviour since I moved from Ventura to Sonoma.I have a 2012 Mac Mini. Ever since going to Sonoma my computer has been hard freezing after a random amount of time. Never had this issue with Ventura.
Upgrade went well for each iteration. I'm currently on 14.2 OCLP 1.3.0. I ran an extended memtest from boot and no issues with memory. Any ideas on how to find the root cause of this? Thanks!
I did wonder if perhaps old faithful was starting to suffer hardware problems, but have managed to rule that out with diagnostics, and also by the observable fact that booting from my Catalina external HD (or even - yeuch - my Windows partition) makes the stability problems instantly disappear. Like you, Ventura (along with Monterey and Big Sur before it) was always totally fine for me.
I updated to 14.2 with OCLP 1.3.0. a couple of days ago and there seems to be an improvement in stability so far, but haven't really used it enough to reliably tell for sure. I see now that 14.2.1 has literally just been released! Yikes! Might wait that one out for a while if 14.2 stabilises things... If not, I figure I have nothing to lose by updating again. I'll also try an NVRAM reset (thanks for the reminder on that 'K Two'!)
I've just accepted this situation as a reality of having an unsupported setup, and if my OCLP luck has run out at this point then so be it. I had a good run!