Never done it in 5e but have done it in 3e. Maybe this could still be a useful couple of examples for you in spite of that.
Lich: wizard, sorceror, cleric, knight, druid, warlock, mystic theurge, any of the (insert planar exemplar species here)-ologist or -erist classes such as diablerist for example, or favored soul levels
Vampire: wizard, sorceror, paladin, knight, rogue, druid, soul eater (a rare class that usually only monsters have. Its actually not homebrew FTR), fighter, crusader, bard, or sword dancer levels
Dragon: wizard, sorceror, knight, paladin, druid, mystic theurge
Ghost: whatever you think would be normal for the race it had while alive up to the age it was when it died, also soul eater
Nymph: druid (obviously), if the nymph is the descendant of a recent godly ancestor, double the levels by pairing druid levels with favored soul levels.
Demon: any of the thrall class levels (as thralls typically will become a demon at some point), warlock, sorceror, rogue, barbarian, fighter
Devil: knight, sorceror, wizard, domain wizard, crusader (redo the spells somewhat), paladin (redo the spells somewhat)
Celestials: cleric, paladin, favored soul, crusader
Modrons: knight, crusader, fighter, factotum
Aboleth: warlord, wizard, sorceror, practically any psionic class (but i dont touch psionics classes myself), any ologist or erist class (give them a lot of racial bonuses to these classes features due to the unique manner in which aboleths inherit memories which is unmatched in other species, its also the main reason ilithids cant eradicate aboleths. The advantage is that big.)
Ill probably post more later but at the moment i have to attend to something.