A debrid service downloads torrented content upon request and stores it for a set amount of time. By connecting the API key of an account from a service to a Stremio plugin, users have access to most content that's otherwise available on regular subscription services. Popular shows and movies get requested by users often, and are therefore generally available on demand without the need for the service to re-download it.

Some debrid services (such as Real-Debrid) are more likely to make content unavailable due to DMCA requests; some (such as Torbox) are less likely to. If a service starts complying with DMCA requests at a more frequent rate, it's easy to switch providers.

Various guides to setting Stremio up with a debrid service are available, such as this one.

All that said, if there's a European competitor to Crunchyroll, it's good to support them too.