documentclass[a4paper,12pt]{article}
usepackage[greek.ancient,italian]{babel}
usepackage[T1]{fontenc}
begin{document}
Dal grecobegin{otherlanguage*}{greek}
br'aqistos
end{otherlanguage*}(brachistos), ebegin{otherlanguage*}{greek}
qr'onos
end{otherlanguage*}(chronos), tempo.
end{document}

usepackage{gentium}

usepackage[sc]{mathpazo}
usepackage{substitutefont}
substitutefont{LGR}{rmdefault}{udidot}
linespread{1.05}

usepackage{newtxtext}
usepackage{substitutefont}
substitutefont{LGR}{rmdefault}{txr}

documentclass[a4paper,12pt]{article}
usepackage[greek.ancient,italian]{babel}
usepackage[T1]{fontenc}
usepackage{newtxtext}
usepackage{substitutefont}
substitutefont{LGR}{rmdefault}{udidot}
begin{document}
Dal grecobegin{otherlanguage*}{greek}
br'aqistos
end{otherlanguage*}(brachistos), ebegin{otherlanguage*}{greek}
qr'onos
end{otherlanguage*}(chronos), tempo.
end{document}

$ find /usr/local/texlive/2019/texmf-dist -name lgr*fd | wc -l
42

./tex/latex/cbfonts-fd/lgrcmr.fd
./tex/latex/cbfonts-fd/lgrcmro.fd
./tex/latex/cbfonts-fd/lgrcmss.fd
./tex/latex/cbfonts-fd/lgrcmtt.fd
./tex/latex/cbfonts-fd/lgrlcmss.fd
./tex/latex/cbfonts-fd/lgrlcmtt.fd
./tex/latex/cbfonts-fd/lgrlmr.fd
./tex/latex/cbfonts-fd/lgrlmro.fd
./tex/latex/cbfonts-fd/lgrlmss.fd
./tex/latex/cbfonts-fd/lgrlmtt.fd
./tex/latex/cm-lgc/lgrfcm.fd
./tex/latex/cm-lgc/lgrfcs.fd
./tex/latex/cm-lgc/lgrfct.fd
./tex/latex/comfortaa/lgrfco.fd
./tex/latex/droid/lgrfdm.fd
./tex/latex/droid/lgrfdr.fd
./tex/latex/droid/lgrfds.fd
./tex/latex/epigrafica/lgrepigrafica.fd
./tex/latex/gentium-tug/lgrgentium.fd
./tex/latex/gfsartemisia/lgrartemisia.fd
./tex/latex/gfsartemisia/lgrartemisiaeuler.fd
./tex/latex/gfsbaskerville/lgrgfsbaskerville.fd
./tex/latex/gfsbodoni/lgrbodoni.fd
./tex/latex/gfscomplutum/lgrcomplutum.fd
./tex/latex/gfsdidot/lgrudidot.fd
./tex/latex/gfsneohellenic/lgrneohellenic.fd
./tex/latex/gfsporson/lgrporson.fd
./tex/latex/gfssolomos/lgrsolomos.fd
./tex/latex/kerkis/lgrkfn.fd
./tex/latex/kerkis/lgrmak.fd
./tex/latex/kerkis/lgrmaksf.fd
./tex/latex/lxfonts/lgrllcmss.fd
./tex/latex/lxfonts/lgrllcmtt.fd
./tex/latex/miama/lgrfmm.fd
./tex/latex/opensans/lgrfos.fd
./tex/latex/opensans/lgrfosj.fd
./tex/latex/tempora/lgrtempora-tlf.fd
./tex/latex/tempora/lgrtempora-tosf.fd
./tex/latex/txfontsb/lgrtxr.fd
./tex/latex/txfontsb/lgrtxrc.fd
./tex/latex/txfontsb/lgrtxry.fd
./tex/latex/txfontsb/lgrtxryc.fd

documentclass[a4paper,12pt]{article}
usepackage[greek.ancient,italian]{babel}
usepackage[T1]{fontenc}
usepackage{newtxtext}
usepackage{substitutefont}
substitutefont{LGR}{rmdefault}{porson}
begin{document}
Dal grecobegin{otherlanguage*}{greek}
br'aqistos
end{otherlanguage*}(brachistos), ebegin{otherlanguage*}{greek}
qr'onos
end{otherlanguage*}(chronos), tempo.
end{document}

documentclass[a4paper,12pt]{article}
usepackage[greek.ancient,italian]{babel}
usepackage[T1]{fontenc}
usepackage{newtxtext}
usepackage{substitutefont}
substitutefont{LGR}{rmdefault}{artemisia}%%%%% You must delete from %%%lgrartemisia.fd, lgr to have only artemisia. Same for every font of the list of %%%@David Carlisle.
begin{document}
Dal grecobegin{otherlanguage*}{greek}
br'aqistos
end{otherlanguage*}(brachistos), ebegin{otherlanguage*}{greek}
qr'onos
end{otherlanguage*}(chronos), tempo.
end{document}