Recently, the way to specify fonts at the top level changed.
Now you do fonts = (; regular = "Times New Roman", bold = "Some bold font"), there’s also italic and bold_italic in the default theme but that’s not used anywhere so far. You can also define your own font categories if you want. Check this page: https://docs.makie.org/stable/documentation/fonts/#symbol
Makie should in principle find all fonts that FreeType can read which reside in the typical font directories on Linux, Windows and Mac. If you have fonts stored somewhere else, for example in a specific project asset directory, you can always use the path to the font directly like regular = "./assets/fonts/special_font.otf".