@Fragglemuppet they're both forks of Mastodon that increase the functionality  Glitch-soc is a bit more common, while Chuckya is specifically used by wetdry.world, if memory serves  

since you've excluded other microblogging software like misskey (+sharkey) and akkoma, I'm wondering if you're narrowing it down to very specifically vanilla Mastodon to the exclusion of all else or if you're talking about Mastodon and its forks but with other microblogging software excluded 

fairly large instances like tech.lgbt that a lot of people think of as "mastodon" are actually running Glitch-soc, so it can make a difference