I have done the following operations on my machine.
Go to this font squirrel, download the following TTF files (TrueType font file):
lmroman10-bolditalic-webfont
lmroman10-bold-webfont
lmroman10-italic-webfont
lmroman10-regular-webfont
lmromanslant10-bold-webfont
lmromanslant10-regular-webfont
Navigate to this System Folder:
C:\Program Files\Mathematica12.1\SystemFiles\Fonts\TrueType
Paste the ttf files to this folder.
Restart Mathematica.
Now when you style text, as when using PlotLabel
, AxesLabel
, TicksStyle
etc.,
you can use the rule
FontFamily -> "Latin Modern Roman 10"
when applying Bold styling, lmroman10-bold-webfont.ttf
will be used, and when applying an Italic styling, lmroman10-italic-webfont
will be used.