Ninjaman - Black Screen when level should start
In Ninjaman, after the title screen there is a second play button, after which the screen goes black and a brief "Loading" message appears, before the level starts. In Ruffle, the screen goes black but it never says "Loading" and the level never starts.
https://www.newgrounds.com/portal/view/289067/format/flash?emulate=flash
Other note - the menu screen has a faded overlay on top in Ruffle, making it look washed out.
The swf is trying to load a bunch of off-domain http files, this might be a case for http->https upgrading
Unfortunately the website that this game relies on to load its level files no longer exists. It works in Flashpoint with the FPL-Ruffle extension though. The visual issue with the menu screen still exists.