Installing on ubuntu lxc proxmox container

Hello, wich repository i can use?

root@mattermost:~# curl -o- https://deb.packages.mattermost.com/repo-setup.sh | bash
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 6078 100 6078 0 0 10950 0 --:–:-- --:–:-- --:–:-- 10951
ERROR: Unsupported ubuntu release: “lunar”