Both mupen64plus and GlideN64 are extremely active, with tons of development going on (apparently Indiana Jones just recently works, as does World Driver Championship finally).
I today raised this issue and it turns out 3 games that are completely unplayable in the mupen64plus-libretro core are fixed upstream (Cruis’n Exotica, Fighting Force, Duke Nukem: Zero Hour).
Just wondering if we could get a core update sometime? 
Oh wow, that’s really sad news. Compared to Parallel, this core is virtually plug and play and aside from the issues I’ve mentioned, extremely usable, with most games completely playable. No messing with plugins or anything. 
I still use the older Glupen core before the name changes. Apparently the current Mupen64 core has frame rate issues in some games (like Mario 64) that were already fixed in Glupen but now came back for some reason.
And now reading the above posts makes me lose hope about N64 emulation in RA 
@GemaH if you look at the Github issue you’ll see that twinaphex wants / intends to do a core update. It’s just he’s massively busy.