"As of late" or "as of lately"?

"Lately" and "as of late" are synonyms. You would not combine them in the form "as of lately". It's worth remembering that "as of late" is a formulaic construction that doesn't allow just any old adverb of time to be substituted. As of now, as of then, as of six o'clock — all these are acceptable time expressions.

As for usage, I don't like to go to the NGrams viewer, but it definitely shows that "as of lately" flatlines in comparison to "as of late".

Neither. I can find no reputable dictionary that accepts "as of late." The expression you want is "of late," meaning recently or lately.

There is "of late" and there is "as of [specific time]". *"As of late" is an uneducated muddling of the two.