Those running a public server:

UNSUNG Project Delta
Project Delta, special forces recon unit and official beta testers
(Don't judge us by the public servers!)
https://units.arma3.com/unit/unsung-project-delta
teamspeak.armanam.eu
Demo gameplay:
https://www.youtube.com/watch?v=Q2CaQQyuVl4
1st Cavalry Division
http://1stcavalry.org/index.php?/page/index.html
Public Server: gs01.1stcavalry.org:2328

173rd Airborne Brigade 'Nam
https://steamhost.cn/steamcommunity_com/groups/173rdNAM
Public Server: 192.187.117.2:2322

As well as other groups, units and communities:
5th Cav - TS IP: 151.80.47.181
7th Cav - https://7cav.us/
1/5th Marines - clockworkhosting.ddns.net
433d TFS, 8th TFW - (Available to reach in our discord: https://discord.gg/2RXqmjb )
B/2/502 101st - https://steamhost.cn/steamcommunity_com/groups/B2502 & 85.236.100.121:11967
C/1/502 101st- fp280.teamspeak3.com
75th RRC - TS IP: 74.91.127.221

PVP Communities that will be organsing more UNSUNG stuff in future:
OFCRA - https://ofcrav2.org/forum/index.php
Frontline - http://frontline.frl/