I installed Metabase on DigitalOcean by using the following link: https://marketplace.digitalocean.com/apps/metabase.
I already did a lot of research (for example this link: https://www.metabase.com/docs/latest/operations-guide/customizing-jetty-webserver.html#using-https-with-metabase), but nothing helps. I can only serve it through port 3000 and HTTP.
Any help is really appreciated. Thanks a lot!
I would highly recommend not using that marketplace app - it's very outdated.
You should setup Metabase yourself - example by following this guide:
And then you can enable LetsEncrypt via Nginx by following one of DigitalOcean's many tutorial: