There were lots of Portal Gun mods on 1.7.10 and 1.12.2, but hardly any for new versions. This one brings see-through portals, no loading screen, 7 guns, turrets and Long Fall Boots to Fabric & NeoForge 1.21–26.3.
HBM's Nuclear Tech Mod on 1.21.1: a backport of NTM: NEXT. Reactors, nukes, radiation and heavy industry, and all of it flies on Create: Aeronautics airships. Unofficial build.