I cannot seem to get a handle on changing my cinnamon theme from those already on the Cinnamon Spices site to one that I have downloaded. I loaded it into /usr/share/themes and it would not show up. I put the theme into ~/.themes and it also didn't show. I also noticed that /usr/share/theme contains several themes that LinuxMint put in /usr/share/themes and they don't show up.
I'm sure I am missing a minor factor somewhere, but I cant find it.

According to quick search as of October last year you got it right, ~/.themes so maybe: "Mint settings doesn't show ~/.themes"—as a search, e.g: https://forums.linuxmint.com/viewtopic.php?t=328288

What version of Mint? 20.?

I didn't look into it past copying that link. I don't use Mint, for my tastes too many middlepeople but run into the same issues on Debian. So-many crisscrossing settings,
not that we aren't to blame?

It's actually 20.1. I think I might have stumbled onto my problem. The first thing I did wrong was when I uncompressed and moved the file into the .themes dir, I didn't notice that the actual files were actually 1 step further down than the ones supplied in the archive. So once I took care of that it seemed to be ok.
I also noticed (after digging down past the named dir) that the other themes in that were supplied by Mint were actually gtk2 themes and not named cinnamon. And my guess is that the gtk2 files wont work just by simply dropping it into the dir.
I;ll just keep plodding along till I figure it out. Thanks to all for looking into it with me.

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