Voadam
Legend
I'd have a hard time saying any of those explanations was narratively non-magical, even with technically not being suppressed in an anti-magic field. Leaking holy power out of every orifice does not seem non-magical.Let’s try looking at this in a different way… At level 11, paladins get improved divine smite. Each of their attacks does an additional 1d8 radiant damage. One interpretation is that they are so holy, they are leaking holiness out of every orifice.
This isn’t magic. Improved divine smite works in an anti-magic field. It can’t be dispelled or counterspelled. It is part of the paladin’s nature.
Smites can work in the same manner. Particularly since the basic smite doesn’t even need to be “cast” the way other smites are.
I prefer to leave that to the individual players. Maybe one will tie it to their weapon being blessed. Maybe another will tie it to their righteousness (the same way a monk’s ki empowers their extraordinary abilities). I would love it for a genasi paladin to tie it to the manifestation of their racial heritage and express it as fire, cold, lightning or acid damage instead.
None of them are close to "I am just non-magically good at hitting things." The closest might be Captain Planet heart style righteousness powering smite damage, but even then the radiant energy aspect kind of begs for an explanation if you stick with non-magical.
You could go with there is just holiness of the person that comes forward at points and cosmically wrong things react badly to it (vampires stop regenerating, etc.) but that kind of does not really work if you smite a bear as holiness does not generally narratively translate to general damage.
I mean for monks, thinking of ki as non-magically powering extra attacks or better dodging can work. Ki powering street fighter fireballs seems magical.