That’s really odd. I tried the same in an empty project, and got a different error for Distributions.jl, but the net result is the same.
What’s odd about the quoted line is that there is no compatiblity setting in the Project.toml file of ApproxBayes.jl which restricts StatsBase.jl to versions below 0.33.21. A newer version would work just fine.
The same thing happens with Distributions.jl for me: it restricts it below 0.23.12, but the dependencies work just fine with the newest 0.25.117.
ApproxBayes.jl hasn’t been updated for a while, but that shouldn’t be an issue.
Furthermore, if you run pkg> dev ApproxBayes, it adds the dependency just fine.
Update: apparently, the master version on github is slightly different from the registered 0.3.2 version, in that it has a few compat entries. I don’t see how adding some restrictions solves the problem, but apparently it does.
Update 2: Okay, found it. The problematic compatibility values come from the registry itself. It’s the registry entry of ApproxBayes.jl which limits the versions of StatsBase.jl as <= 0.33 and Distributions.jl as <= 0.23. The package should be bumped and reregistered.