Have you been playtesting the One D&D rules documents from Wizards of the Coast? Try these options for inspiration!
One Better: Inspiration Aspirations - Kobold Press
Paizo Kobold Press Vault of Magic for 5e: Larwood, Phillip, Lockey
Archetypes Archives - Kobold Press
Dungeons Are Half the Game., You can’t control what players are going to do. That’s half the fun. But you can control where they do it. That’s a
Kobold Guide to Dungeons
Kobold Press's Tome of Heroes - A Review
5 Tips to Make a Dark Campaign Setting
Creature Codex — Stygous
Kobold Guides Kobold Press Kobold Guide To Worldbuilding, Volume
Monster Philosophy - Kobold Press
Matt Carlson: Gen Con 2021 – RPGs
Southlands Campaign Setting - Endzeitgeist
Divine Purpose, part 3 - Kobold Press