While Minecraft has visible quite some mods seeing that its 1.0 launch again in 2011, we’ve found out of one that hasn’t simply been executed until now.
The mod, BetterPortals, helps you to pass thru each Nether and End portals without a loading display, or even works on both normal portal shapes and custom ones too.
Due to the loading-slicing nature of this mod, it has incompatibilities with other mods like Portal Gun, Cubic Chunks, and others. Render has to be disabled, and Render Region can’t be used near portals. Shader mods additionally have troubles.
Similar mods have tried over time, but have been by no means completely found out.