Ah! I think I see the confusion.

# /etc/subuid
privatenoob:100000:65536

This denotes the range of subuids that are available to your user.

-u 100000:65536

This part specifies two things ([UID]:[GID]) even though it’s the same syntax as the earlier part that specifies one range :)

I suspect what you will want to do is use the following:

# change ownership of the directory to the UID:GID that matches something in your subuid:subgid range, in this case 10000:10000
podman unshare chown -R 100000:10000 /home/privatenoob/media/storage1/Filmek/

Then we can specify that the user in the container can match the user (UID) we specified above:

ExecStart=podman run --name=radarr -u 10000:10000 -p 7878:7878 -v radarr-config:/config -v /home/privatenoob/media/storage1/Filmek:/data --restart unless-stopped lscr.io/linuxserver/radarr:latest

As a note, if you copy/pasted that ExecStart line, you might have gotten the invalid argument error because you entered 100000 (outside of your subuid range, i.e. >65536) instead of 10000.

There’s a nice guide that gives a great walkthrough. I’ll dig through my bookmarks and add it here when I get some time.

Hope this helps!