Is it a mod compatibility issue?

Yes

If it's a mod compatibility issue, please provide the link(s) to the incompatible mod(s)

https://www.curseforge.com/minecraft/mc-mods/pehkui

Minecraft version

1.20.2

Describe the issue

It tried to put immersive portals and Pehkui in the same folder but it crashed when I booted up minecraft and it's clearly the mod because I renamed the installation to immersive portals

Pehkui does not support 1.20.2 and it crashes in 1.20.2 without ImmPtl Virtuoel/Pehkui#455
It's not an issue of ImmPtl.