You can view the entirety of Quake or view a specific Quake game and find out the best time to hop on so you'll have a better chance at facing real players.
Heres August so far:
* 1,009 peak concurrent players (Aug 16), 504 on average
* 978 servers hosting real matches - meaning 2+ humans and an actual frag, not just an idle server
* 7,891,962 frags scored by real players, counted between polls
* 123,902 hours of Quake played
* Twitch: 54 streams live at peak, 1,803 viewers at peak, plus a leaderboard of the top streamers
Also on there: the busiest servers and most played maps, top gametypes/mods/countries, and a world map of where people are playing
You can view the whole page here - https://quakehub.net/state-of-quake