Cleric: fixed typos relating to bonus spells elemental affinity
Ranger: moderate fixes as the ranger's default 1st level powers can largely render exploration and survival without challenge.
Favored terrains changed to match Dark Sun terrain
Favored enemies modified to remove celestials, dragon, and fey
Auto navigation modified to Advantage on check
Bypassing difficult terrain modified to ranger-only
Rogue: cosmetic text changes
Breakage: reduced % chance from 10% (1-2 in d20) to 5% (1 in d20). Non-metal weapons were still breaking too often. Matches % chance from original AD&D. A d4 bone dagger goes from chances of 1 in every 40 hits to 1 in every 80 hits.
Wild Talents. Complete overhaul to make them more engaging, useful, and in-line with original AD&D psionics.
Updated druid wild shape list to match fixes to monster manual.
Changed errata that druids do assume the entire stat block of creatures (RAW), including innate powers such as psionic. This fits with the Crag Cat (SKT) which had supernatural features and maintains the CR of the creature.
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.