macOS Sequoia on iMac 27 (mid-2011)

After trying different approaches I managed to boot into Sequoia on this 14 year old iMac. It seems to work just fine, without any noticable hiccups. The only issue is... I can't boot it without the usb stick plugged in. Anyone managed to solve such an issue on this specific setup? I even tried blessing the ssd manually, but didn't succeed.