

KasmVNC is basically a completely different solution. It’s browser based, has authentication (although regular vnc does as well), and they’ve made significant improvements to performance by using libjpeg-turbo instead of the normal image libraries.
When using the docker containers (e.g. the webtop linuxservio oned), I noticed no lag for non-gpu accelerated sessions over the internet.
Edit: although it’s not your definition of rootless though.
Actually I just realized that’s not true. it is possible to serve a single app via kasmvnc. It’s still web based though.
It’s quite fast, I recommend you try it.
https://docs.linuxserver.io/images/docker-webtop/ – these are all in one docker containers that include kasmvnc and some apps, but you can also deploy kasmvnc independently.