I am installing the mod on 1.15.2 and as you know, Ars Nouveau has three dependencies Curios, Patchouli, and Geckolib 2.0. I installed the three mods as listed, and launched my Minecraft as usual but "Geckolib" was listed as not installed. I made sure that I have installed all three mods. I tried uninstalling the mods, restarting my pc but nothing seemed to work out. I am still facing the issue of not being able to launch Minecraft because of Geckolib being listed as not installed.

latest.log

1.15 requires geckolib 2.0, mod launchers automatically install 3.0. You will need to manually download 2.0.