I have written a Mathematica function (DispLaTeX) that uses ImportString from LaTeX format, and then some postprocessing (converting the Cells, BoxData, and TextData, etc.) It does not use an external library, so it does not produce as nice an output as MaTeX, nor does it implement all of $\LaTeX$, but it is lightweight and does not require installation.
Style[DispLaTeX["$$f\\!(x)=\\sum_n\\left(x^n/n\\right)$$"], FontSize->16, FontFamily->"Latin Modern Math"]
produces

applying InputForm gives
Style[DisplayForm[RowBox[{StyleBox[RowBox[{}]], StyleBox[FormBox[RowBox[{StyleBox["f","I"], "\[NegativeThinSpace]", RowBox[{"(", StyleBox["x","I"],")"}], "\[LongEqual]", UnderscriptBox["\[Sum]", StyleBox["n","I"], LimitsPositioning->False], RowBox[{"(", RowBox[{SuperscriptBox[StyleBox["x","I"],StyleBox["n","I"]], "/", StyleBox["n","I"]}],")"}]}], TraditionalForm]]}]], FontSize -> 16, FontFamily -> "Latin Modern Math"]
$FontFamiliesto get a list of all font families available. Is"Latin Modern Math"indeed in the list? Perhaps it has a different name. See also MaTeX package. – Domen Jul 29 '23 at 14:18$FontFamiliesand check it, please. – Domen Jul 29 '23 at 14:31