bewCloud doesn't offer any server-side or end-to-end encryption (only in the HTTPS/SSL sense, and that's from caddy in the recommended docker-compose.yml file).
I also created and maintain an open source end-to-end encrypted product, Budget Zen [1], and it's just a different kind of beast.
Applying either concept here would be very complicated and complex.
To get an idea, Nextcloud offers server-side encryption and end-to-end encryption add-ons (apps), but they often cause issues with data becoming irrecoverable [2] [3] or simply not being compatible with mobile/desktop apps or other plugins/apps. And they have many years, many people, and a lot of money to throw at the problem.
[2] https://help.nextcloud.com/t/recover-encrypted-files-after-l...
[3] https://help.nextcloud.com/t/all-files-lost-after-encryption...