Hi pearofducks,
Nice try ! =D But yes ... I did ...
Can you confirm that mattermost need his own vhost ?
In this case i would like to see an exemple of vhost for mattermost ...
EDIT : Ok, so i tried to install mattermost without Gitlab integration and i've found a vhost here : https://github.com/mattermost/platform/blob/master/doc/install/Production-Debian.md
It seems to work fine now. 