In OpenID there is no well supported way to log out users from services which used the OpenID for authentication (in Cloudron case the apps). Those app have their own session and session handling. So there is mostly likely no way around this unless an app would start using OAuth2 access and refresh tokens (but implementation of that was spotty in the past which sparked OpenID connect in the first place)
For a start if you logout of the dashboard, subsequent app logins (from a state where the app has no login session) then Cloudron will prompt you to login with a username. If that is not happening the Oidc session was still alive.
The best way I found was to use container tabs in like firefox and probably other browsers, which maintain isolated sessions. This is also how I use other services like Digitalocean where we have multiple accounts with different roles.