Admittedly, I haven't looked at any open-sourced firmwares either which could have improved things.
I have found the Sispeed USB KVM very useful, the convenience is well worth the $50 it cost me. The UX isn't great but you don't really need it to be. It works (most of the time) via WebUSB for the keyboard mouse.
I will say iDRAC has been a lot more reliable for me, but the chance I'll ever buy a Dell server for home use is basically 0.
Most employ heavy compression by default, and it looks a little more pronounced with motion. A few have 'high quality' mode, but especially on the Pi-based KVMs this eats up more CPU, so I don't use that.
It's on the whole best for use cases where you just need to log into remote servers and check on things, or reinstall/re-image something. I don't think I'd like using any of these for a constant remote session for daily work. I do use Screen Sharing on macOS for that sometimes, and it works great in its low-latency mode. None of the KVMs I've tested are quite to that level.
Barbing•32m ago
Jeff Geerling rocks