IIRC that model doesn't give apps audio route change notifications when Bluetooth is disconnected, which screws up audio timing. Or something similar, each model has different bugs. But yeah, it doesn't spontaneously catch fire, so on Samsung scale it's good. Reviewers generally don't know about this stuff, because app developers have already worked around it.
The S21 Ultra seems like a very good purchase from reviews. QHD screen with dynamically adjusted 120Hz seems really like the best spec.