I'd like to request Backblaze B2 as a an option for backups. It's API is not S3 compatible unfortunately, but it is a cheaper option than S3.
I wanted to suggest Authelia as a way of providing Cloudron with SSO, U2F, TOTP, etc. for all apps, especially those which do not support it natively. It seems like it's already packaged for Docker.
Just something to look into. Having U2F with my Yubikey for all Cloudron services would be pretty sweet.
I'd like to request client certificate authentication as an additional feature. It may not be appropriate for every app, but an option to enable it for some would add a great extra level of security.