So I just recently got an iMac and the only change I’ve made to it since it got into my possession was replacing the mechanical HDD with a new Samsung 860 EVO SSD and it worked for about a day without issue. Now anytime I try to boot into Mac OS, a Mac OS USB installer or online recovery it just gets stuck at the Apple logo loading screen. In verbose boot I can see two particular errors that seem to be of possible interest:
WARNING: IOPlatformPluginUtil : getCPUIDinfo: this is an unknown CPU model 0x5e
and shortly after
kextd stall[0], (240s): ‘IGPU’
Yet I can boot/install Windows without issue (though I would like to run Mac OS)