I tried the http://www.pdf995.com/samples/ and brave did open the pdfs in a new browser window, all good.
Reading the thread you shared Clicking on PDF links will prompt to save file instead of allowing to open it I conclude that the issue may be with special characters being encoded using % , while I did not test too many, I know that the pdfs I am having this issue with do have such encoding issues (being named with greek font).
Still a shame that brave did not manage to solve this yet.