From "Applicable Resource Types" appendix:
Other ActivityPub types, such as activity types, are less likely to have their own HTML representations.
I don't think this is a generalizable statement that can be made. Activities as content may be less likely on the Fediverse, but other deployments of ActivityPub can and do give activities their own HTML representations, usually with the design pattern of "activity streams".
From "Applicable Resource Types" appendix:
I don't think this is a generalizable statement that can be made. Activities as content may be less likely on the Fediverse, but other deployments of ActivityPub can and do give activities their own HTML representations, usually with the design pattern of "activity streams".