#(actually google's own previously bard now gemini)

[aeolianblues]

COME ON, MAN

PS if it wasn't widely clear already, looking to text generators for 'answers' is the most useless thing you'll do

And if you were looking for an actual answer, I worked it out from the dictionary. Largely they are extremely interchangeable as they're both nouns, but 'sincerity' is classed as a mass/uncountable noun, which means in theory you could hypothetically have multiple sincerness-es, but there is no hypothetical plural of sincerity, so forget the whole thing because nobody has ever used those words that way. Synonyms. Google gaslighting you to think there's a difference by putting a 'however' between calling them both nouns ffs