Reach wan from guest network

I have an HTTPS web server running on one of the devices on my lan and a port forward from wan to this server. That works fine. The service is accessible from outside. It is also accessible for devices on the LAN at the public (WAN) IP address. Unfortunately it is not accessible from the guest network.

I’ve been trying to find why. The main thin in Luci Network/Interfaces I can find is that the LAN includes wlan0 in the Physical Settings and the guest network does not. There doesn’t seem to be an option to add wlan0 to the gust network and I have no clue whether this is a good idea. Before this I had dd-wrt (pretty old version) where it was capable to access the WAN address from the guest network.

This runs on a brand new Turris Omnia, runnong Turris OS 5.1.3

Any clues? Thanks!