I have tried fabric and forge, and both versions of the mod are rendering the portal red in the nether and blue in the overworld. Is there something I'm doing wrong? Could it be because I'm using a third party launcher?

Maybe your videocard does not support some GL features. Try using command /immersive_portals_debug front_clipping_disable

Maybe your videocard does not support some GL features. Try using command /immersive_portals_debug front_clipping_disable

This didn't seem to help. Is there anything else I can do?

Probably nothing. The critical GL feature is not supported there and the portal cannot be rendered.

Probably nothing. The critical GL feature is not supported there and the portal cannot be rendered.

If I use a launcher that uses a different renderer could that help? One such as zinc or osmesa?

I don't know