Speaking about Prusa, my experience has been that they’re very condescending to users.
Extremely basic features (like serial printing) are considered “nice to have”. Some tickets have remained open for over 6 years now and ignored by prusa:
- https://github.com/prusa3d/Prusa-Firmware-Buddy/issues/189 (still open after 6+ years)
- https://github.com/prusa3d/Prusa-Firmware-Buddy/issues/283 (took 3.5 years to acknowledge and fix)