Psionics, added Psionic rules link to the Korranberg Chronicles on DMs Guild. The best I've found thus far that creates an independent system, with 2 new psionic classes, 3 subtypes (fighter, monk, rogue), monsters, NPC stat blocks, and a reasonable list of talents (core psionic power) and their augments (enhancements to core powers once those core powers are activated). For those seeking a free resource, version 3 of the mystic remained linked. Removed the text for the mystic, reducing page count.
Psionics, clarified that effects that detect or cancel magic also affect psionics. Effects that help with saves against magic or reduce damage do not affect psionics.
Thri-kreen, base AC to 13 instead of 12. Consistent with AD&D kreen, clarified they cannot wear anything designed for humanoids, including armor and rings. This limits them heavily when it comes to magical items (carried only). Added innate psionic talent to be consistent with Korranberg design and AD&D design.
Half-giant, hit point boost reduced from 2 per level to 1 per level, retaining initial 2 boost.
Half-elf, tweaked animal charm to be consistent with other charms
Wizard, removed familiar boosts; it was added bookkeeping for minimal gain
Warlock, expanded list of patrons and their sources
Monks, clarified for elemental source of powers, can lose them per cleric rules
General, consistent with original AD&D design, fiends are permitted on Athas, but no other outerplanar creatures. The reason for this exception is unknown except perhaps to the sorcerer kings and queens.