Ok so you got me curious :) since I only know ligatures as, in my simple understanding, two glyphs that are joined together for typographic (visual) purposes. Googling 'dental fricative', that seems to be about phonetic spelling. Would you mind explaining? Is the unicode code point for a 'dental fricative' the same as the bytes of t and h in succession? How does the ligature fit in?

I can't properly explain something I was wrong about.

But yes, "dental fricative" is the "th" sound made by pressing your tongue against your teeth. An example would be the sound in "teeth", written "ti:θ" with the international phonetic alphabet. I assumed someone had read about how, say, "the" was once written "þe" and gone off to restore the usage, as certain people are wont to do. Except that would be overly confusing, so I further assumed that what they found was instead a ligature, a combination of two letters for mostly shorthand and visual purposes, here for the digraph "th". Turns out that there is no such unicode code point - the visually closest thing I can find is ᵺ, and as seen above, it's not even a symbol for the fricative.