PostScript Type 1

They do still work, but there are limitations.

1. If you use Font Book, you won't notice anything wrong since it copies all fonts (by default) to the user account Fonts folder, or the root /Library/Fonts/ folder, depending on how you have Font Book's preferences set. T1 PS fonts placed either of these two folders still work as expected.
2. If you use a font manager other than Font Book, and you enable fonts in place, or the third party manager stores copies of the fonts you add to a location other than the user account Fonts folder, or the root /Library/Fonts/ folder, then they don't work. You get blank lines where the fonts should alphabetically be listed in the font lists of apps such Quark XPress, MS Office and others.

But T1 PS font's days are numbered. Starting sometime in 2021, Adobe is dropping all support for them beginning with Photoshop. I would expect the rest of the CC suite will follow close behind.

Also, as the Adobe article mentions, some apps are already ignoring T1 PS fonts, even though Big Sur itself will still let you enable them.

Looks like Big Sur turned all of my T1 Outline fonts to green and black Exec icons, but the 16 Type 1 fonts in my ITC Garamond suitcase are unscathed, and remain available on the Pages v10.3.5 font menu.

That's rather bizarre!

I erased the external SSD I was running the beta on and then installed the official public release of Big Sur. After that, I manually copied five randomly chosen T1 PS font sets into the user account Fonts folder. There's not a lot of OS installed apps I could test them on, but they did appear in Font Book and worked as expected in Mail and TextEdit.

I didn't doubt you, I just haven't seen that happen. Why is it doing that? Couldn't say off the top of my noggin. I see the OS recognizes the suitcase (it at least has an icon), but the printer outlines are all borked. Do they have a size, or have they somehow all been trashed to zero bytes?

You also have a mix of sets with only one of the three suitcases there should be. The ITC Garamond fonts should be in three separate folders, per their original distribution. Bold text is the suitcase name of each set.

ITC Garamond 1

GaramBol

GaramBolIta

GaramLig

GaramLigIta

ITC Garamond 2

GaramBoo

GaramBooIta

GaramUlt

GaramUltIta

ITC Garamond Condensed

GaramBolCon

GaramBolConIta

GaramBooCon

GaramBooConIta

GaramLigCon

GaramLigConIta

GaramUltCon

GaramUltConIta

The type of issue you're having is one of the reasons I never, ever install a new major OS release over an older one. It does take a while to reinstall all of my third party apps and set their preferences, but I also never see 1% of the issues users report here. It has to be a true error with the new OS, or incompatibility with third party app that needs an update. I don't have to try and figure out what mix of the old OS and new may be causing a problem.

That, and I can continue to work in the previous OS until I'm done installing everything, and tested thoroughly to make sure every app is working. Typically, I wait until at least the .1 update before I'll commit to the new OS. It'll take at least that long I think for some apps I need to be updated for Big Sur. Like USB Overdrive, the Wacom tablet drivers, and a few other things I know the vendors have said they're still working on.

I did install Office 365 into Big Sur about an hour ago and tested more T1 PS fonts. No issue using them, as long as they were placed in the user account Fonts folder. Doesn't matter if you do that through Font Book, or just put your fonts into that folder manually.

Don't laugh too hard, but that ITC Garamond font suitcase originated with Illustrator 8.0.1 from 2000, and may be the result of my running some forgotten (maybe FontAgent Pro) font utility on classic macOS that aggregated all of these Garamond fonts into one suitcase.

Heheh! I think that's where my sets are from, too. I copied a whole bunch of T1 PS fonts off of the installer CD to keep.

Having worked in a few large print shops, I think I've seen just about every way a client could mangle T1 PS fonts. They'd stick Windows .ttf and .ttc TrueType fonts into a Mac T1 PS suitcase. And sometimes the outline fonts, somehow expecting that to work. Or they'd send us lots of printer outlines but no suitcase. Or a suitcase that had some, but not all of the screen fonts needed so all of the supplied printer outlines would work. And lots of badly modified fonts because someone didn't like the kerning pairs as Adobe or Linotype had them, but would also send an unmodified version that would conflict with the hacked font. Lots o' fun!

Actually, a phase out of postscript fonts was started last fall.

I had to stop using a font, Euclid Symbol, as Apple took over the font and substituted with a TrueType.

Best solution... just replace any Postscript fonts with OpenType, which have a much larger glyph pallet.

Voila…

I believe they are no longer supported, and you will need Trutype, OpenType-Truetype, or OpenType-Postscript replacement fonts.