documentclass{article}
usepackage{mathtools}
newcommand{diff}{symup{d}}
newcommand{npder}[3]{frac{partial^{#1} #2}{partial #3^{#1}}}
newcommand{vect}[1]{symbfup{#1}}
usepackage{luaotfload} %% only for use with LuaTeX
usepackage{unicode-math}
setmathfont{STIX2Math.otf}
setmathfont[range={scr,bfscr},StylisticSet=1]{STIX2Math.otf} %% line A
setmathfont[range={int},StylisticSet=8]{STIX2Math.otf} %% line B

begin{document}
begin{gather*}
   symcal{L} = -incrementsymcal{U} = -qincrementsymcal{V} \
   incrementsymscr{E} = symscr{Q} - symscr{L}
end{gather*}
begin{align*}
     &int_0^{+infty} frac{5x+1}{3x^2-x-10} ,diff{x} = \
   = &lim_{alpha to 0^+} left[ frac{2}{3} left.lnleft(3x+5right)right|_0^{frac{1}{alpha}} + left.lnleft(2-xright)right|_0^{2-alpha} + left.lnleft(x-2right)right|_{2+alpha}^{frac{1}{alpha}} right] = \
   = &lim_{alpha to 0^+} -frac{5}{3}lnalpha = +infty
end{align*}
begin{equation*}
   begin{dcases}
      nabla^2vect{E} - frac{1}{c^2}npder{2}{vect{E}}{t} = vect{0} \
      nabla^2vect{B} - frac{1}{c^2}npder{2}{vect{B}}{t} = vect{0}
   end{dcases}
end{equation*}
end{document}