@jor2404 The Link you quoted is from 2 years ago, this option probably already exists in the latest version.
See this emulator page in the official documentation:
https://wiki.recalbox.com/en/emulators/consoles/nintendo-64/libretro-parallel_n64
If you search for "upscaling" you will find an option that should be this one.
In the retroarch menu of recalbox paralell core there isnt that option
I'm not sure, but maybe this option is intentionally disabled on your hardware, as developers sometimes block options that are incompatible with the hardware to avoid crashes caused by users' misconfigurations on hardware that doesn't have enough power. (Or, you're using an outdated version of the system, you haven't made it clear neither your hardware nor the version of Recalbox you're using, so I'm just guessing).
According to the documentation this option can be used in a Configuration override file, but unfortunately N64 is a heavy emulator for cards up to Rpi3, it starts to perform better from Rpi4, so be careful with some options.