Hello,
Backuply doesn’t fully supports multisite it can backup/restore multisite, but currently it creates backup of whole multisite installation, you can exclude the database tables of different multisite, but those settings reflect globally for all sites, so if you want to create backup and restore whole multisite installation then Backuply will work smoothly, but if you want to keep backups of single sites in a Multisite installation, you will need to exclude the tables of other website, and add note for that to keep track of that.
We hope that clears your query.
Regards,
Backuply Team