Multi-seat, single-user, single-session environment

Question

I'm looking for a way to use my desktop normally, be able to lock it (with dm-tool, i3lock, or whatever), and log in to that same desktop remotely and continue working with my running graphical applications.

I've experimented a bit:

• x11vnc does nearly what I want, but I can't figure out how to lock the main terminal/seat/display and continue using the virtual one.

  (Adding a second, virtual display and deactivating the main one might work, but I'm unsure how to handle, mouse, keyboard, and other possible periphery.)

• lightdm's vnc feature: Gives me several sessions, on top of that those sessions die when the VNC client dies.

Using the terminology of systemd, what I want should be a ulti-seat, single-user, single-session environment. I'm not really set on using anything specific, neither the mentioned vnc, lightdm, or even X11 are really necessary. The only thing I'm set on is a tiling WM and linux…

Is there maybe some login manager which I can get to vnc-connect to an automatically started, virtual desktop running in background? Or am I missing something and I can get lightdm to lock the main screen while x11vnc stays being accessible?