regarding NC 19.0.3. with Polls App 1.4.3, behind reverse proxy.
When used to find a meeting date it mails out a backlink that uses the internal ip address as host. Other funktions like sharing a file via e-mail work as expected using the configured name to use for NC behind reverse proxy dealing with ssl and certificates.
Afaik, it’s in the responsibility of the app developer to update the app store accordingly.
If possible, don’t use ip addresses in your configuration because it could usually break e.g. the certificate verification of a secure server access, instead use the fqdn of your server.
You’re most likely right, but I don’t know how the app has been programmed. An open issue ticket still exists, which addresses this issue: