The main issue with backing up Podman appdata when using Quadlets is that first we need to stop all services with systemctl --user stop <service_name> which we need to run without sudo; otherwise it will not work.
Then we need to back up all appdata files with sudo rights because some files do not have read permission for others group.
Finally, we have to start all containers with systemctl --user start <service_name> which again must be run without sudo rights.
My solution is to use 3 separate scripts:
stop-podman-services.shincrontab -eruns every day at 5:00 AM;backup-podman.shinsudo crontab -eruns every day at 5:02 AM as root. We have a 2-minute buffer to allow all containers to stop;start-podman-services.shincrontab -eruns every day at 5:06 AM. We give 4 minutes of buffer to allowtarto finish its job. This buffer should be adjusted if there are many services.
The solution is not ideal in my opinion. I would prefer to run all the commands in one script. One solution is to allow a script that requires sudo rights to be run as a non-root user with sudo rights without requiring a sudo password, which poses a security risk if for any reason that script is modified for nefarious purposes.