Still having this issue more than 24 hours later. Why isn't there some kind of announcement from "those in the know" about what is going on, and when it is expected to be fixed? Some who posted here have had this issue for over 2 days now. It seems to me that the right thing to do is for somebody to make some kind of an announcement, at least something like "Hey, we know there's a problem, we're looking into it."

Thanks for the hint. I installed a Korean font and now I can see it. Yay! [BTW, how can you tell it is rendered on your system via a Chinese font?]

Thanks to everyone who took the time to help.

Tried these fonts (I like them) but it's not fixing the box. I know the system is picking it up because I noticed the difference. I'm ready to give up. But thanks for the nice fonts.

Do I select "All locales"?

Mate is my DE, and what you describe is found in Control Center >> Appearance >> Fonts tab, and the "Application Font" setting (I already knew that). I tested every font on my system just now (a tedious task), and not one of them got rid of that box.

The thing is I had this file when I was on Devuan 4 (a Miyo install, but added Mate, just like I did for Devuan 5, a Crowz install, but added Mate) and there it displayed correctly. Also, I have a list (a long one) of every file/app to install that applies to Mate, so, besides being on a different version of Mate (1.26 vs. 1.24) everything else is the same as far as Mate is concerned. That leads me to believe that something is different in the OS install, and that this is "probably" not a Mate issue. Then again, I'm not an expert, so anything I think is just a educated guess.

EDIT

Okay, I just thought of something that is different. Miyo did not install with a word processor, so I had added LibreOffice. Crowz installs with AbiWord, so I didn't bother to install LO. I think (but I'm not sure) an install of LO also pulls in a ton of fonts. I wonder if I install LO if that would solve this. I really don't want to, as LO is bloatware compared to AbiWord. Do you think it's worth a shot? Or am I off base here?

Yeah, I already tried installing fonts-noto-core but that didn't fix it.

When connecting my cell phone (yes, I have one and I hate it) I don't get any thumbnails either. I wish I knew what to install for it, if anything.

I'm beginning to wonder if it's even worth it to disable it. What could (theoretically) happen leaving it enabled?

I found it just as you were responding.

Here's what I see in / and /boot. What do I do with info -f grub -n 'Simple configuration'? I tried that in the terminal and nothing happened (sorry for my ignorance).

Thanks to everyone who replied. Everything is recognized when I log into the Mate DE.

Yes it is missing (in Mate, I don't remember if it is missing in Openbox). But these 2 apps you mentioned are already installed. I remember having this problem last time with a Mate install. I just manually create a link on the desktop to Trash and find a suitable trash icon for it. Thanks.