I made the transition smoothly. I emphasize that I didn’t have any major issues because the number of images or backups was minimal. The forum was entirely for testing purposes, not yet in “production”.
Finally, after several trials and errors, I reinstalled the forum on a new server (Hetzner) and configured Cloudflare S3 R2 (previously, I had Amazon S3), for backups and images with the server that finally convinced me.
I’m sorry I can’t be much help. I’ll see if I can test it on another server in the future.