Hiya, have you tried the method listed at the top of FAQ? Make sure you set the capture method to "windows 10 and up" and tick the "allow transparency" box.
I have yes and that didn't seem to do it
If the rahituber window itself is transparent, then that can only be a bug with OBS, I'm afraid. The other option is to use the Spout2 plugin.
okie pokie, thanks for the help either way!