prevent changing of permissions in mounts with rootless container

I think --user $(id -u):$(id -g) --userns=keep-id will get what you want.

$ id -un                                                                                                                                                                                                                                      erik                                                                                                                                                                                                                                          $ id -gn                                                                                                                                                                                                                                      erik                                                                                                                                                                                                                                          $ mkdir x                                                                                                                                                                                                                                     $ podman run -v "$PWD/x:/x:Z" --user $(id -u):$(id -g) --userns=keep-id docker.io/library/ubuntu:focal bash -c 'mkdir -p /x/1/2/3 && chown -R nobody /x/1'                                                                                    chown: changing ownership of '/x/1/2/3': Operation not permitted                                                                                                                                                                              chown: changing ownership of '/x/1/2': Operation not permitted                                                                                                                                                                                chown: changing ownership of '/x/1': Operation not permitted                                                                                                                                                                                  $ ls x                                                                                                                                                                                                                                        1                                                                                                                                                                                                                                             $ ls -l x                                                                                                                                                                                                                                     total 0                                                                                                                                                                                                                                       drwxr-xr-x. 3 erik erik 15 Sep  6 19:34 1                                                                                                                                                                                                     $ ls -l x/1                                                                                                                                                                                                                                   total 0                                                                                                                                                                                                                                       drwxr-xr-x. 3 erik erik 15 Sep  6 19:34 2                                                                                                                                                                                                     $ ls -l x/1/2                                                                                                                                                                                                                                 total 0                                                                                                                                                                                                                                       drwxr-xr-x. 2 erik erik 6 Sep  6 19:34 3                                                                                                                                                                                                      $ 

Regarding deleting files and directories that are not owned by your normal UID and GID (but from the extra ranges in /etc/subuid and /etc/subgid) , you coulduse podman unshare rm filepath

and podman unshare rm -rf directorypath