Musescore 3 FreeSans bold text rendering is bad
Came up in https://musescore.org/en/node/281541
The reason most probably is that we don't package a Bold (nor Italic or BoldItalic) version of FreeSans (but do for FreeSerif) and that converting a normal font to Bold generally gives rather bad results (not so much for Italic, IIRC)
As per https://www.fontspace.com/gnu-freefont/freesans, https://en.wikipedia.org/wiki/GNU_FreeFont and https://www.gnu.org/software/freefont/ there is a FreeSans Bold and a FreeSans Oblique and a FreeSans BoldOblique (Oblique rather than Italic, but seems to be the same thing), and also a Free Mono family.
So the fix would be quite easy(?): add those fonts to the package.