The plugin says it should work on 1_19_R1 (includes 1.19.3) but does not.
Btw, version states it is 2.0.2, but file itself states 1.0.2.
Error occurred while enabling Rift v2.0.2 (Is it up to date?)
I guess your iris plugin that supports 1.19.3 but not multiverse, will not work in 1.19.3 either, because Rift doesn't. (Multiverse is the working alternative and mainstream world manager.)
It's simple and effective to load just worlds, but there is no way (that I know of, also asked in discord and support told me it isn't possible) to link nethers and ends with their overworld counterparts.
In my case, I wanted to hace a resource world with its own nether and end, sepparated from the survival world. Problem is, when you enter portals in the resource world, instead of sending you to resource_nether o resource_the_end, it sends you to the main worlds dimensions.