Java is version 1.8.0_241, using 64-bit architecture.

--fml.forgeVersion 31.1.44

Mods:
[✔️] JAOPCA-1.15.2-3.2.0.8
[✔️] Mekanism-1.15.2-9.9.19.411
[✔️] SilentGems-1.15.2-3.5.1+84
[✔️] SilentLib-1.15.2-4.6.0+48

I got the following crash report :
https://pastebin.com/MZABm95d

Full log :
https://pastebin.com/JUp7GYwr

If I remove any of the above mods, the game launches correctly. It seems that it is not a Mekanism issue ( mekanism/Mekanism#6056 )

Edit : Crash with Mekanism 412 too. Crashlog mentions JAOPCA.
https://pastebin.com/Rg8hnw56

I am getting the crash that looks the same in the last link.

According to the Mekanism dev response to the Mekanism Issue I posted (which is the same error as this one), this relates to changes to the Mekanism Gas API. JAOPCA will have to update for compatibility. (see Mekanism Issue #6063)

Yes, same issue here: https://pastebin.com/4CpSPFKf

Fixed