First troubleshooting steps:
1. Copy here the first ten lines of Help > System Info, so we can verify you haven't been struck by a nasty upgrade bug.
2. Edit a raw file (not a JPEG or TIFF) in Develop -- do the presets show up?
3. In Finder, do the menu command Go > Go To Folder and enter the following:
replacing username with your username. Expand the subfolders and paste a screenshot here. It should look similar to this:
Thank you for your assistance. I apparently didn't have any raw files in the catalog. I imported a raw file to edit and the presets showed up fine.
I imported a raw file to edit and the presets showed up fine.
This is a design misfeature that's tripped up lots of people: Lightroom Classic: Presets including raw profiles are sometimes available for non-raws, sometimes not | Photoshop Family…
Your presets have the Treatment & Profile option checked, which included a raw profile in the preset. And since the raw profile can't be applied to JPEGs, LR 7.3 and later won't display the preset or let you apply it to the JPEG (even though earlier versions of LR would).
The workaround is to update the settings of each preset, unchecking Treatment & Profile.