In incus, I had the same setup of an LCX container with a Docker container inside of it. I passed 1000/1000 to the LXC container and but the LXC container’s default root user has a an ID set of 0/0. So I had to pass 0/0 to the Docker container, not 1000/1000 to get the read/write permissions working.

That may fix your issue as it’s basically the same tech, just different automated things implementing the LXC container!