I'm not an old school sacrifice player, I discovered it around a year ago and I absolutely love it. I've seen a lot of Discussions both on Steam and GOG about some unofficial patch and an active discord server that houses the sacrifice community. But, the unofficial patches don't work for me, and all the discord server invites already expired. :(
Is the Online community still going? and if so, how can I join it?

No idea if the community is still active, but here's working discord invite link: https://discordapp.com/invite/CTkCPnZ
Source: https://steamcommunity.com/groups/ShinyEntertainmentSacrifice2000#
Have fun!

Thank you!

Unofficial multiplayer patch has no use any longer. The server it was redirecting to is gone for over 4 years. It was hard to convience some people that this patch was not a virus. Some people said they got alert from their AntiVirus softwares. We even show them the difference in the code of the original Sacrifice.exe file and the changed one. For now people talk in discord and look for someone up for games and play using "zerotier" or "hamachi".