Would it be possible to add a class to the body when you are navigating to a category with ActivityPub enabled?
The markup for the topic-list of the activity pub view is slightly different from other core pages in Discourse, causing some themes to not style this page correctly.
An example of which can be seen here on meta when using the meta-branded
theme and visiting → Discourse Meta
Normally, the top nav area is wrapped in list-controls
And under it is wrapped in list-container