What is the highest average charisma skill check a solo character can get, without using magic?

I was building a character that had levels in Feywanderer ranger, that gains Otherworldly Glamour which allows you to add wisdom to charisma checks, and then I noticed Samurai fighters get Elegant Courtier which has the same bonus.

Emboldened by the fact they stack, I started to look for other class features that let you reroll failed intimidation checks or gain advantage.

It made me wonder, what is the highest possible charisma skill check by a solo character?

(This means no spells, or magic items and no outside assistance except by summoned/created creatures, e.g. a familiar using the help action is ok, but a party member using flash of genius is not.).