Last year I said I'd probably never recommend another Bambu Lab printer again.
I still use my P1S, but after Bambu Lab started pushing their always-connected cloud solution as the new default:
I blocked the printer from the Internet via my OPNsense Firewall I stopped updating the firmware I locked the printer into Developer mode I deleted Bambu Studio and started using OrcaSlicer I had to do that to keep it under my control, instead of Bambu's.
Well, the most open you can get is Prusa’s machines. Repairable, upgradeable, with great customer service to boot.
Other companies are more open than Bambu but few support the open-source movement like Prusa. Qidi, Elegoo, etc. all have great printers that I can recommend (Q2 and Centauri Carbon are fantastic options based on feature set) but they don’t use a very open firmware. They are compatible with OrcaSlicer and aren’t as bad as Bambu though.