I’ve had some level of success using “gluetun” as the host of the container you want to hit, for any container outside of gluetun’s network mode.
Then, for those that are sharing the gluetun network, they can communicate using their regular hostname but using the internal port instead of the published one.
Out of all my containers behind gluetun I have only one that hasn’t been able to connect with anything but IPs
“You can’t expect pears out of an elm tree” or “No le pidas peras al olmo”