you can try
mtxrun --script font --list --info garamondpremrpr ... to see what happens with features
Thanks. This seems to confirm that the features are there: MTXrun | dnom cyrl dflt MTXrun | grek dflt MTXrun | latn aze crt deu dflt fra ita mol rom srb trk MTXrun | numr cyrl dflt MTXrun | grek dflt MTXrun | latn aze crt deu dflt fra ita mol rom srb trk MTXrun | ordn cyrl dflt MTXrun | grek dflt MTXrun | latn aze crt deu dflt fra ita mol rom srb trk MTXrun | sinf cyrl dflt MTXrun | grek dflt MTXrun | latn aze crt deu dflt fra ita mol rom srb trk MTXrun | sups cyrl dflt MTXrun | grek dflt MTXrun | latn aze crt deu dflt fra ita mol rom srb trk but still, \definefontfeature[body][default][script=latn,onum=yes,pnum=yes,calt=yes,protrusion=quality,expansion=quality] \definefontfeature[in][body][sinf=yes]%inferior \definefontfeature[su][body][sups=yes,ordn=yes]%superior \definefontfeature[nu][body][numr=yes]%numerator \definefontfeature[de][body][dnom=yes]%denominator in {\addff{in}123} su {\addff{su}123} nu {\addff{nu}123} de {\addff{de}123} produces only proportional oldstyle figures.