Setting PUID and PGID to root

I can’t say I have made the same experience.
This is the compose I used for docker:

version: "3.7"
services:
  unifi-controller:
    image: docker.io/linuxserver/unifi-controller:version-6.5.55
    container_name: unifi-controller
    environment:
      - PUID=1000
      - PGID=1000
      - MEM_LIMIT=1024M #optional
    volumes:
      - /opt/Unifi:/config
    network_mode: host

Running this compose via podman-compose with the command

podman-compose -f ./docker-compose.yml up -d

results in these kinds of errors

chown: changing ownership of '/config/data/backup/6.0.23.unf': Operation not permitted

(There is more of these, just didn’t wanna fill the entire page with them)
If I exec into the container the mounted files appear as the following permissions:

root@container:/usr/lib/unifi# ls /config -la
total 20
drwxr-xr-x  5 root root 4096 Dec 23 14:07 .
dr-xr-xr-x 21 root root 4096 Dec 23 14:04 ..
drwxr-xr-x  5 root root 4096 Dec 23 14:03 data
drwxr-xr-x  3 root root 4096 Oct  3  2020 logs
drwxr-xr-x  3 root root 4096 Dec 23 14:04 run

On the host these files have the owner of the user I run the container with, which makes sense that they then would be mapped to root:root inside the container.

I’m not sure why this problem occurs, as the container should run as root initially, but changing the PUID/GUID to 0 seems to fix the issue.

Are you by chance running podman with sudo or root in your setup ? Because that would work for podman to access these files and run pretty much just like docker, but I don’t think that counts as rootless.