@l @sjw @p @Moon definitely, the code to hack is
https://git.pleroma.social/pleroma/pleroma/-/blob/e8d35256653d196fd7c0daba8673a74dfe40a8e8/lib/pleroma/web/activity_pub/activity_pub.ex#L664

the simplest way would be to fetch activities from the DB as normal
and then if there's not enough activities
fire off a GET /api/v1/accounts/:id/statuses request to their instance, iterate with Pleroma.Object.Fetcher.fetch_object_from_id(id)
and redo the DB query

figuring out the max_id=pagination might be a bit complicated though, the id's being snowflake<time,rand> might make up for it though

@alex thoughts?