Allowing users to add themselves to a private channel (not using roles)

Goal: Ability for users to show only channels they care for (and hiding all unwanted channels from them)

There is a way how a user can add himself to a private (hidden) channel through reaction roles, but this is not suitable for managing a big number of individual channels -> too many roles.

We have a student server of our faculty and want to have a channel for each compulsory subject for each offered study field. This is a lot of channels (approx. 200) which would bloat up the whole sidemenu. Another problem is that we cannot divide them into categories by study fields, since many subjects overlap across them - there would be duplicates of channels this way.

Is there another way how a user could add himself directly to a private channel (eg. using reactions or commands) without creating that many roles?

PS. A feature that would allow simple hiding (not muting) of channels would be a life saver!