Shame-they did so much work according to the datamines only to throw out the most thematic and defining characteristic of the class.
As noted Paladins do not choose deities in 5e -- they choose Oaths.
The only character in 5e that chooses a deity is a Cleric.
I know folks want some things from previous editions of D&D but mods are likely the best place for that content.
Multiclassing As a Paladin/Cleric is tricky as you need at least a 13 in Strength, Charisma, and Wisdom.
If no mods are available you can always name your character "Tav servant of Helm"
Except there's stuff even in 5e that suggests this is not the case, like how you are expected to redeem a fallen paladin by finding a priest of the same faith. We had a big 'ol thread about this previously-it's not that clear-cut.. If that divide between 5e and earlier paladins becomes more defined in the future, then that's one thing-fanon becoming canon, I guess. But Larian by all indications was ready to give us Paladin deities and chickened out at the last minute