This wasn’t known to me when migrating from local to S3 storage. It isn’t possible to use a different S3 provider for backups than the main storage, meaning a full migration of the main storage would need to be done to use an alternative provider for backups.
Scaleway may be rolling out a fix (can see in the post I linked to), so rather than needing to rebuild several times with downtime just to check if it is working, I’ve been letting it try to succeed on a weekly basis, seeing that the backups that don’t successfully upload are kept in the local backups folder anyway.
It doesn’t, as I stated in my post. IIRC the message saying it will be removed still appears in the log, but that is not what happens in reality. If anyone is interested in understanding this edge case bug, I can check/confirm.