The feature to have Categories as the front page is now available. In a community where users are only interested in a certain category and don’t care about the rest, is there a way to set this up in Discourse? Or possibly a mod or plugin to accomplish this?
For example, each category is a sport, e.g. basketball, football, etc. Upon logging into Discourse, the user goes to football as the default first page defined during sign up or under preferences setting.
Pls be nice. My first post. 
Welcome @TopQuark!
Check out GitHub - pfaffman/discourse-custom-homepage-for-groups: Discourse theme component to change home page based on user's primary group, which I suppose I should make a post in theme for. A client combines it with GitHub - literatecomputing/discourse-ucf-group-assignment: Update group membership based on user custom field to allow users to choose a value in a user custom field which automatically assigns them to the group which the theme component then uses to select their home page.
^^^ This is great. A quick look shows this is what I am looking for. 
I have discussed with @sam and @eviltrout an end state where users select just the stuff they want to see (collection of tags / categories) as “their” feed, as in /custom.
We already have the ?tracking path for this:
https://meta.discourse.org/unread?f=tracked → unread in categories you track and topic you track and tags you track
https://meta.discourse.org/new?f=tracked → new
https://meta.discourse.org/?f=tracked → everything
The support for the special param is there in core, there is just no UI to expose it. We only expose it in “teams”.