My theory is Wayland happened. As SPICE doesn't work that well through it. I would assume it's another case of a "niche" the Wayland protocol didn't account for, however.
Interesting theory. Any idea on why SPICE wouldn't work well through it? I don't have recall running into any issues with it.
A more Wayland-oriented remote desktop protocol would probably make for an even better VNC alternative, but I don't really know why SPICE never got the uptake it deserved.
Wasn't aware SPICE was deprecated. However, I think it addresses a different use-case than RDP: SPICE is primarily designed for accessing virtual machines by connecting to their hypervisor. Thus it's designed to operate without VM guest awareness nor cooperation, going purely from a framebuffer.
This approach is fundamentally limited in terms of performance/responsiveness, as you're ultimately just trying to "guess" what's happening and apply best-effort techniques to speed things up, falling back to just using a video stream.
A proper remote desktop solution like RDP on Windows works in cooperation with the OS's GUI subsystem in a way that makes the RDP server aware of the GUI events, so it doesn't have to guess, and can offload compositing and some 2D operations directly to the client, rather than sending rendered bitmaps.
Thus it didn't catch on because it focuses on a narrow use-case nobody should be using except in emergency/break-glass situations (you should instead be remoting into the VM directly, for reasons explained above), and even for such situations, it didn't offer anything substantial over VNC, except everyone and their dog has a VNC client by now, but good luck finding a functional SPICE client for anything but Linux.
They installed a root certificate on windows computers that could have been used to MITM all traffic.
I personally had issues with the project years before that when I tried to install their Linux .deb and they ran `pip install` as root in the pre install script inside the .deb. That caused so much havoc to clean up I was pissed at them for years. Now that idiocy is blocked by default in current versions of pip.
