In general, you can find the logs from documentation generation on the JuliaHub info page for the package behind that circled ⓘ. I’m not 100% sure what went wrong in this case, but I think it might be a version mismatch between Julia and/or the packages that are installed as you build the docs — I think your GitHub docs builder uses Julia v1.6 whereas JuliaHub is using v1.9.
In any case, if you host your own docs, you can opt out of the documentation building by telling DocumentationGenerator where your docs are — and @pfitzseb just did that! That gets a bit at the goal here: it’s really useful to be able to know where all the docs are for multiple reasons (including: ecosystem search, a theoretical @ref macro here, ability to get docs offline, etc.), and while there are a number of significant improvements needed (and planned!) for JuliaHub’s doc generation.