Unreal
Unreal
It would be better to join the old Unreal Tournament (pre-alpha) instead. It's completely free! https://www.epicgames.com/unrealtournament/
The game isn't great by any means; it lacks the vibe of earlier versions, which makes it hard to know if many players are still around.
UT99 remains active with quality music and maps. It closely resembles UT4, though UT99 offers its own unique vibe. I favor UT3, which still supports online players. It includes bots and a simple single-player narrative with narration. UT3 features intriguing artwork and provides enjoyable gameplay for a short time. It isn't the top-tier experience, but it stands out visually and atmospherically. If you own it and wish to play online, I'd enjoy participating in a few sessions.