>>106127585Firefox v134 -> v 135 changed how certain font families are rendered.
v134 had a built-in blacklist that prevented DirectWrite + Cleartype font rendering from being used with certain fonts that were never designed for it and forcing them to be rendered with legacy GDI + Cleartype rendering.
v135 removed that list because of overall improvements to the new font-rendering stack making it 'acceptable enough' and Mozilla wanting to cut down on costs of maintaining GDI rendering, by eventually axing it.
https://bugzilla.mozilla.org/show_bug.cgi?id=1924346#c2
You can probably still temporarily reinstate the old rendering, but eventually it will be removed entirely.
Your best bet is fine-tuning the DirectWrite/ClearType rendering to not suck.
gfx.font_rendering.cleartype_params.cleartype_level 100
gfx.font_rendering.cleartype_params.enhanced_contrast 50
gfx.font_rendering.cleartype_params.rendering_mode 5
gfx.font_rendering.directwrite.use_gdi_table_loading false
That should be it to get it to work reasonably for those legacy fonts, without noticeably impacting modern fonts, iirc.
(And yes - FUCK Mozilla for the horrible transition on this and basically bomb-dropping it on users.)