I already spotted Fools, they say i was born a kings daughter and Adonis so I imagine there's a handful more.
I think something like this has happened before but with a youtube channel where they uploaded episodes after they were released on tapas. I think a good start would be to report this if possible on the site, though whether or not the folks there would listen is unknown especially given the fact that they're uploading these comics (as far as we know) without permission.
I'm not sure about the process either but there should also be something within the DMCA that would make their actions illegal. Like I can google "Fools Webtoon" and there's a lot of results that pop up but also the note at the bottom that looks like this
"In response to a complaint we received under the US Digital Millennium Copyright Act, we have removed 1 result(s) from this page. If you wish, you may read the DMCA complaint that caused the removal(s) at LumenDatabase.org."
It's honestly a pain when stuff like this is constantly happening but it always seems to happen on such a large scale 