You should maybe try the Search function. While it's certainly niche, it's not wholly unsupported in OGL works, and there's plenty of old work on the topic that still holds up.
Wow, say it with more condescension why don't you.
But hey, let's see what happens when I search "Plane of Salt" in the DMs Guild.
1) Citizens of Saltmarsh -> Nope, not the plane of Salt.
2) Codex of the Infinite Planes Vol 03 Plane of Earth -> Sure, I bet it
includes the plane of salt, but it isn't an adventure set there.
3) Map pack for Invasion from the Planet of Tarrasques -> Nope
4) Daerdan's Tall Tales: 101 Seafaring Encounters -> Plane of Salt doesn't have a sea, sooooo... nope.
5)
6)
...
11) Oh look, here is the Inner planes book for 2e that just mentions the plane and isn't an adventure for it.
12)
...
23) Monster Loot - Curse of Strahd
...
Got all the way down to 50 entries, using that Search function, and not a single adventure set in the plane of salt, or a book devoted to the plane of Salt. And considering I started getting things for Curse of Strahd within the top 50, and there were only 125 results... I don't think I'm going to find it.
So, please, tell me again about this magical search function that will show me what doesn't seem to exist?