@alexanderkings I haven't finished the step of migrating this to a Cloudron app, but I've been using mole to securely forward ports between networks using SSH Private/Public keys. My Docker implementation is Dockamole.
I'm using it already outside of Cloudron to allow my VPS to scrape metrics generated on my home NAS.
The workflow would require a Server container running on Cloudron and then a Client container running on whatever machine you'd like to access the forwarded port. All services on that machine access the service through the local container and it's forwarded to the server container.
Like I said... I haven't gotten it running on Cloudron yet though.