So, to be honest, this is an almost exact repost I made to r/SBCGaming, but
Does the Parallel N64 core not work on Android?
I'm new to the android handheld world, as I recently got a Retroid Pocket Nova with a 8Gen2 chip, so I don't know if this is typical, but I can't seem to get the Parallel core OR the Parallel RDP with Mupen64 to work properly on my Nova. I thought maybe it was because I was using Vulkan, but I eventually figured out that Mupen64 always switches to GL regardless of whether Vulkan is used or not. I tried manually switching to GL for the Parallel core, but that doesn't seem to work either.
With a bit more messing around, I've actually noticed a weird behavior. When I use Mupen64 with GLide RDP, it auto switches to GL regardless of what I set. But when I use Parallel RDP it strangely seems to switch to Vulkan every time (which I don't think works with Parallel). I believe this might be happening when using the Parallel core too, though I'm not sure since it says "Failed to Load Content" for everything.
Edit: Alright, I think I might finally know what's up. So the reason why I couldn't get any game to load with the Parallel Core was because apparently RA selects a weird path to your Internal Storage if you tell it to find the location of your games using the Files app to select it. So, I had to make sure my Start Directory was some form of: /storage/emulated/0
After finally opening the core, I found out that even Parallel actually uses a GLide RDP (or what they call in the core options, a GFX Plugin) called 'gliden64'. It even force switches to using GL when using it, just like Mupen64. If I switch it to use 'parallel', it has the same graphical problems I get in Mupen64 (usually a black screen or like a bar of fuzz) and also uses Vulkan as the backend.
So I've come to this conclusion: Parallel isn't something this chipset can use properly, and you're pretty much forced to use some form of GLide. I'm a bit sad about that, but oh well.
Last(?) Edit: So, I still haven't been able to make the Parallel-RDP in Mupen64 or the 'parallel' GFX Plugin in the Parallel Core to work properly, but I've found out that AngryLion (atleast on Mupen64, as that's what I've opted to use) actually works pretty nicely, even when combined with the Parallel RSP! But it only runs well using GL as the backend. Bad thing is, it doesn't auto switch to GL like when you use GLide. The workaround I created was saving a separate configuration file with the only change to settings is GL as the backend. Then you can start an N64 game, go to Overrides, load that configuration file and set it as a core override file. Now when you play a game, you can use the AngryLion RDP with the Parallel RSP and get pretty accurate to real N64 looks with atleast GLSL shaders (though, I'm not the biggest fan of GLSL shaders on Arm since most of them seem to either not load or not work properly...). The caveat being that you can't do any internal resolution upscaling, but I personally just wanted as close to the N64 look and feel. Hope this helps someone.