I just gave it a shot, since my Minio instance is just holding a few backup files that are not mission critical (until the worst case happens...).
In case anyone is wondering how to change the used image, first add the following line to /etc/default/openmediavault
Then execute the following commands (not sure, if they are all necessary and correct me if there's an easier way)
And lastly, since I didn't know how to restart a service from CLI (other than running "podman restart minio-app", which - I presume - would start the same image again), I briefly disabled and enabled S3 in the OMV UI.
Added benefit for me is, as mentioned in the linked Blog post, that the Admin functions in the Minio Web UI are back. I was not happy when those vanished last year.