When trying to host a multiplayer game no content are displayed only following error:
Deleting matchsettings.mp.json helped. (for me it was located at ~/.var/app/com.play0ad.zeroad/config/0ad/config
This was the content of matchsettings.mp.json when it was broken:
BTW: FAQ wasn't helpful finding matchsettings(.mp).json. In Linux: find ~ -name "matchsettings*json"
Here's the main log: