WoW Private Server Population Report (2021-05-01, weekend) - over 90k concurrent, archived : r/wowservers
WoW Classic server list: which is the best vanilla World of Warcraft realm for you?
WoW Wrath of the Lich King Classic server populations in 2023 (November) - Dexerto
Classic WoW Realm Populations - December 2019 - Server Population Graphics at the start of 2020 - YouTube
WoW Classic & WoW Classic WotLK Server Population
Server Population - Why don't we organise a massive movement to flesh out the other servers? We just need to do this a community. We don't need Blizzard. : r/classicwow
WoW Private Server Population Report (2021-05-01, weekend) - over 90k concurrent, archived : r/wowservers
Vanilla WoW is POPPING OFF - Server Population 2023 - YouTube
Changes in EU Server Population - Graphs : r/classicwow
Some numerical data on server population and faction balance (US PVE & RP servers)
Blizzard expects World of Warcraft: Classic servers to be "more crowded" than ever before. - Inven Global
New realms and updated population caps may change the Classic realm you choose to play on