After rereading the description of the mod, I don't know for sure if the nether portal doesn't work as a feature, but it doesn't light up after building the portal and lighting with a flint and steel.

Game Version - 1.20.1
Loader Version - 1.20.1-47.2.17
Forge
Directly downloaded with Modrinth Launcher

From the server config:

enableNetherPortals = false