"I can follow them, but I don't see any of their content on their profile unless I'm on a browser."
You should be able to see all the posts of a Pixelfed account made after at least one person from your server followed that account. For example can you see the posts on @Iancylkowski ?
If no one on your server has followed or shared them before, then you won't see their past posts, but this is a general issue on all types of account rather than just Pixelfed: