RAW, the half-elf race from the 2014 PHB or the SCAG works, with the notable and unfortunate exception of it losing its total of +4 ability bonuses and needing to use the same +3 as every 2024 background. Effectively, it is a gimped human who took skilled at first level, and swapped out the second origin feat for immunity to charm and magical sleep. Workable, somewhat weak but I've played one in 2024 and it didn't really ruin the game (I don't think it's weaker than the updated dwarf, for instance) and perfectly cromulent for Solasta.