Someone below mentioned adding some more IPs to the trusted_proxies list so I tried that as well without result. The IP I used for the reverse-proxy is the IP listed in portainer under the network for the proxy container. Just to reiterate, the container is running on a different device than homeassistant (technically same device but different VM but that shouldn’t make a difference).
<span style="color:#63a35c;">http</span><span style="color:#323232;">:
</span><span style="color:#323232;"> </span><span style="color:#63a35c;">use_x_forwarded_for</span><span style="color:#323232;">: </span><span style="color:#0086b3;">true
</span><span style="color:#323232;"> </span><span style="color:#63a35c;">trusted_proxies</span><span style="color:#323232;">:
</span><span style="color:#323232;"> - </span><span style="color:#0086b3;">192.168.208.2 </span><span style="font-style:italic;color:#969896;"># IP of reverse-proxy in its network
</span><span style="color:#323232;"> - </span><span style="color:#183691;">192.168.208.0/20 </span><span style="font-style:italic;color:#969896;"># Subnet of proxy docker network
</span><span style="color:#323232;"> - </span><span style="color:#0086b3;">192.168.1.103 </span><span style="font-style:italic;color:#969896;"># HA IP
</span>