Notify_push with docker compose...cannot figure it out at all

notify_push requests must arrive to the cloud from a trusted_proxies so you either force the connection through your external domain and reverse proxy or your allow the internal IP.. your IP looks like a Docker internal IP if you have direct connection between the two containers..

if you completely follow the guide you will find

which likely solves the problem.. if not and the traffic flows through another reverseproxy this one must trust http headers from notify_push (similar config as for Nextcloud)

I don’t think something is wrong with your reverse proxy.. likely it works as expected and doesn’t trust incoming http headers from notify_push.. but it must. it depends on your setup and intention if it’s right or wrong..

please use search and educate yourself.. e.g. read and understand