Sanity check: Nextcloud App with Nginx, internal and external access both run over internet (slow)

[JackBayerTN]

Hello!

First my setup:
rueNAS-SCALE-22.12.3.1 on Server with two Nics, configured to 192.168.178.20 (gui) and ...21
Nextloud App on Truenas Scale, 192.168.178.21:9001
Nginx App on Truenas Scale, 192.168.178.21:30021-30023

What I'm trying to do:
I'd like to use Nextcloud locally as a Fileserver which is also available on mobile apps outside my home network.
For external access I have a subdomain i.e. sub1.example.com pointed to my external IP-Adress (DynDns) and my router forwards ports 80 and 443 to 192.168.178.21:30021 and 30022.
My ngin instance re-routes traffic from this domain to 192.168.178.21:9001 while using letsencrypt. This works fine.

My problem:
I can no longer get access via my local IP adress. I get

This site can’t provide a secure connection​

192.168.178.21 sent an invalid response.

when I try to access the URL.
I added the https redirect in config.php. Doesn't help.

This is problematic because through my subdomain everything is first send to the internet instead of being accessed locally.

If I then activate SSL in Truenas for the Nextcloud App with "Truenas default certificate" I can access locally but no longer externally through my subdomain:

400 Bad Request​

The plain HTTP request was sent to HTTPS port

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nginx/1.23.3

Any pointers on where to look or what to do, to get this working both internally and externally?

My original solution or plan was to have a SMB share for local access which gets exposed through Nextcloud for comfortable external access.
But I never got it working.

Thanks for any advice!
Patrick