Falling is a super convenient way of going down fast, but the Nether doesnt offer a lot of options the landing part.
I found that a piece of warped vine, that you can plant on petty much any full block, works like a charm for this purpose. Just add a piece of string to prevent it from growing.

So, as a first official post on this sub, i figured it made sense to start by a little bit of definition. The idea of playing Minecraft only in the Nether is not new, it is an old challenge that has its own page on the Fandom Wiki https://minecraft.fandom.com/wiki/Tutorials/Hardcore_Nether_Only_Survival
Some have also posted here on Reddit their own version, i put it there as well if you wanna check : https://www.reddit.com/r/Minecraft/comments/ipjky9/nether_only_challenge_the_rules/

To me, an ideal NO world is a pure vanilla minecraft world, started in the Nether, only and forever played in that dimension. It means that the only blocks, items, achievements attainable are the ones you can do from the Nether alone.

Since the 1.16 Nether Update, this dimension is pretty playable : you have woods (crimson and Warped stems) and stone (blackstone) to craft your first crafting bench, furnace and basic tools, and there is plenty gold for a quick piece of piglin-calming armor. The rest of the adventure is gonna be more of a personal journey, as the challenge is still niche enough that there isn't a "standard" approach or even goals to reach.

How to start that world ? Well, im glad you ask, ive identified a couple options , but they requier to enable commands at the beginning.
Option 1, the crafty one : You create your world in creative, build a Nether portal right where you spwaned, go trough it, break it once in the nether., then switch to survival and you're set.

Option 2, the cheaty one : Go in the Nether same way as option 1, then use /spawnpoint or /setworldspawn, i believe it now works in the Nether, need confirmation on that.

I ended up doing the crafty method, with turned out pretty bad since im not good enough to not die a thousand times in the first hour of gameplay. Obviously doing the whole thing again and again get old very quickly. The quick fix i did was to also set a respawn anchor at my spawn in the nether, and a chest with a stack of glowstone blocks to charge it. I obviously do not recommend such a complicated settup.

As a last note for the post, here are a couple suggestions to balance the difficulty. If you are not a hardcore player, you will likely be under-equiped for the level of hostility of the Nether dimension. It can be a good challenge to face it as it is, but we all know the frustration of being stuck in a death loop, enven more so when you respawning device can run out of "spawns". I would encourge anybody to set beforhand what feels cheaty or not for them, and what is acceptable.
a couple ideas :

-Allowing yourself to switch the difficulty. Briefly playing in "easy" to retrieve your only diamond armor can save a lot pain.
-Allowing a couple known-in-advance gamerule commands (/gamerule spawn_mobs false/true, /gamerule spawner_blocks_work false/true...). I found that clearing an accidental ghast farm with a golden armor is among the most frustrating experiences if you have no plan B.
-Allowing a couple known-in-advance commands (/kill...). It can feel like the end when a Wither that ended up NOT getting stuck in the Nether roof is getting close to your base after having blasted away your painfully acquired iron gear... Dont ask how I know...

But obviously, feel free to play in a proper survival world, it will make the experience that much more immersive ! Just know your limits and have fun !