I didn't know about Falling Through before making this, but I've made it now and it's to my exact specifications so whatever >:)

Little utility mod for Resurvival Displaced. Teleports you to the Nether if you fall into the void! Infernal Expansion is a required dependency, as the mod utilises it's /ntp command to function!

Nether Islands or any kind of datapack removing or opening the Nether roof is also advised as Skyfall Teleportation places you far above the roof height.

Config

Created upon first launching with the mod installed.

void_teleports_dimensions will teleport the player to the Nether (or back) if they happen to take damage beneath the y-level value defined by void_teleporting_depth, which is below void height by default for hopefully obvious reasons. If teleportation_skyfall is enabled, the player will fall from the sky and be given blindness and resistance when first appearing in the dimension. Where the player appears and what effects they have applied can be configured via a small datapack tweaking the skyfall.mcfunction and skyfall_effects.mcfunction files respectively. I wanted to make these values alterable directly in the config, but due to how dimension teleportation logic is handled I couldn't - Sorry about that!

Interdimensional Dew

Utilising Crying Obsidian and Infernal Expansion's Moth Dust in a water bottle or potion in a crafting table will allow you to craft a bottle of Interdimensional Dew! Drinking it will allow you to teleport between the Nether and the Overworld - It's single use, though, so use it wisely!

V1.0 (Outdated)

Gamerules:

Void Teleports Dimensions

Falling into the void will teleport the player between the Nether and the Overworld.

Skyfall Teleportation

If the player didn't teleport to another dimension through a Nether Portal (ala falling through the void) They will be teleported to the top of the world.

Skyfall Resistance

If Skyfall Teleportation is enabled, this dictates whether or not the entity is invulnerable for 10 seconds when they first start falling.

Dimensional Travel Blindness

Entering another dimension leaves you temporarily blinded and vulnerable. (Designed to simulate the darkness of the void.)

Void to Nether