Off the top of my head:
Class DLC:
-Illrigger (Updated)
-Blood Hunter (Updated)
-Talent
-Beastheart
-Theruge (Deep Magic 1)
-Witch (Deep Magic 2).
-Vampire (Nightfell)
-Werebeast (Nightfell:Children of The Moon).
-The Firebrand (Nations and Cannons)
Low Level/Max level 10 gameplay
-Everyday Heroes+The Vault Rules Compendium
-Free League's Lord of The Rings 5E
Keith Baker
-Exploring Eberron
-Chronicles of Eberron
-Frontiers of Eberron:Quickstone
Mercer
-Taldorei Reborn
-Martial Archetype: Gunslinger+firearm rules
Animal Characters
-Humblewood
-Animal Adventures+Faraway Seas
Mods
Single Player/Duet Style of 5E
-Beowulf: Age of Heroes(Followers subsystem)
Exploration/Traveling
-Uncharted Journeys (Cubicle 7).
Soulslike 5E/Fromsoft DND Edition
-Dark Souls (The "Base" rules)
-Ryoko's Guide to the Yokai Realms (Sekiro's Prosthetic Arm rules)
-Iron Kingdoms Requiem 5E (Lies of P)
-Dungeons of Drakkenheim(Demon's Souls)
-Steinhardt's Guide to the Eldritch Hunt (Bloodborne+Trick Weapons)
Tabaxi Lore
-Monarchies of Mau 1E
5E Asian Adventures
-Adventures in Rokugan
-Kamon
-Mists of Akuma
-Undying Corruption Player's Guide
Playable 5E Half Dragons
-Legacy of The Dragons: Draconic Player Races and Other Content
Monsters
-Flee, Mortals!
-Monster Manual Expanded Vols 1-3
-Deadly Denizens
-Tome of Beasts Vols 1-3
Everything else
-Kobold Press
That's, so far, everything off the top of my head