I found a broken, untested backwards compatible PS3 model online which ended up costing me just 11€ and it ended up working! It needs a shell replacement but besides that it works without issues and is actually on 4.60 firmware. I'm speechless! : r/PS3
Ps3 cfw 4.60 ferrox installation, tests and description - YouTube
PS4 Firmware 1.72 & PS3 Firmware 4.60 ab sofort verfügbar
Latest PS3 Firmware 4.84 now hacked thanks to "hybrid firmware" release - Wololo.net