For Unifi OS Server (UOS), the procedure was quite more complicated, especially if one cared about preserving the Source IP (since the X-Forwarded-For didn’t seem to be sufficient).
The solution that worked for me was basically to spin up an additional Caddy container in podman.
Using Caddy directly on the host resulted in a Source IP of 127.0.0.1 or 169.254.1.2 in the UOS Server Admin Logs in the GUI 
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You can have a read at my Post over their community forum, although their forum software was so buggy it caused me to lose what I wrote twice 
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