zlacker

Not sure if I'm allowed to link to stuff, but you can find a bunch of alternatives to offerings like these (the most basic being google alerts), both free and paid, if you look for them - especially on sites that exist to list alternatives.

Some let you link accounts, some give you lists of platforms they scan. I've specifically mentioned Discord because there's no easy way to discover communities without being invited, so if you can actually discover relevant Discord communities and monitor discussions (beyond the few sites that aggregate some popular communities), then you have a USP, since most products don't do that, at least in any capacity that people think is worth paying for.