My old server supports compression but the new server does not
Just use gunzip migration.json.gz or 7Zip to unzip the file.
I don't have an export/import command
Upgrade to 2019.8.0.
I have no SSH/SFTP/FTP access
Well that sucks.
If you have access to your database, then you can dump all passwords tables (passwords_*).
Also dump all entries from appconfig where the appid is "passwords".
Then dump all entries from preferences where the appid is "passwords".
Export the server secret with OCC Web (See FTP migration).
Restore all the tables and the server secret on your new Server.
I used the export in the app but the server won't import it
That's because this is not how this works.
If you get the error The file does not contain a valid server backup or
This seems to be a client backup. It can only be restored using the web interface
then you are likely trying to import a backup which was not designed for the server backup.
If you have a backup from the app, then use the app to import it again.
These backups (client backups) are also only for a single user.
Use the guides above to create and export backups properly.
I get Unsupported backup version
Upgrade the app to the latest version.
Downgrading is not supported by backups because it does not work.