I just noticed that adding the mod Extra Simple (a fork of extra utilities that, from what I can read in the code, has been added to the miniature portal compatibility) does not list the option to craft a miniature portal for the underdark and the end of time, even though it should spawn when either of the mods are loaded.
The fork does spawn those dimensions and loading the original extra utilities adds the portals correctly to NEI, as expected. The portals, when obtained through console commands, also seem to activate and work properly with only the fork loaded, but as said before, they’re unlisted and recipeless.