I’ve just read about some horror stories from people buying these. Some can be very poorly cast and full of air bubbles. On some of the Facebook groups, showing any support for the knockoffs results in some swift action from the moderators. They are looked down on pretty sternly.
As for manufacturers, it appears to be a a large mix of them.
This company has a huge line.
https://www.mitchesmilitarymodels.co.uk/
BNA Model World from Australia is a very reputable company to order from and carries a huge selection. Their prices are pretty reasonable. Just do a search for “bust” and hundreds will show up.
Ultracast.ca is from Ontario. They have a line of figures themselves but have also recently started carrying work from other companies. They are very reputable to buy from as well.
Verlinden closed up shop a number of years ago and most of the remaining stock was sold off. I think most of the mold masters were dumped. There was a few pictures floating around showing molds/masters/ and built dioramas all getting tossed into dumpsters. Sadly at they end the company was not what it was in the early years.