Work in progress on a fix: Add migration code for BoltDB to SQLite by mheon · Pull Request #27660 · containers/podman · GitHub
Noteworthy: this will land in Podman 5.8 in February. It will be removed in Podman 6.0 later in spring, as the codepaths for BoltDB will be entirely gone. Thus, any upgrades from 5.x to 6.0 will need to make a stop at 5.8 to make use of the upgrade functionality.
Our ability to test complicated migration scenarios is also limited. I don’t think there’s a risk of data loss as written but the migration may not be perfect.