Can I migrate from Appstle subscriptions to Seal Subscriptions

Yes, of course. The migration from Appstle is actually really simple, as our app recognizes the export from Appstle without any issues. 
To migrate from Appstle to Seal Subscriptions, simply follow our migration instructions in Seal Subscriptions > Subscriptions > Bulk import subscriptions. In there, they select Appstle as the platform you are migrating from (see screenshot) and detailed migration instructions will show up.