Comment by MrDrMcCoy

The GTK file picker, which is frustratingly the default even on most KDE installs, is the one that sucks. The KDE-native one would much more closely match the experience you're looking for.

VNC is highly dependent on implementation. Sunshine/Moonlight runs circles around RDP in terms of performance and includes audio. For situations where you need the extra functionality is RDP... You can just use RDP. It works just fine on Linux, especially if you're on recent KDE.

On-screen keyboards are admittedly a pain point, but I've usually seen people say nicer things about the screen readers than Windows. Probably lots of different experiences depending on implementation.