No Previews after installing 14.0.1

An annotated copy of your screenshot:

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   First up, is this actually the location of your current catalog? And is perhaps some info missing, perhaps located below what is visible?

• Second up, if this is where you are keeping your working catalog, then it appears you have placed it on the cloud. That is not supported, that will lead to catalog corruption, that will effect performance
• Third up, it appears you are keeping backups and working copies in the same location, in the same media. That is poor practice. If you loose this media, you loose everything. Backups should follow 3-2-1 principle, Three backups on two different media (two different hard drives for example)  and one off site (cloud works for that).
• Those older catalogs and supporting files, are they backed up? Why do you need them if they are backed up?
• At the top, Previous Catalogs, so are these files all old stuff?

The very old thread you found (there are lots of more recent threads) is still completely valid. The 'catalogname previews.lrdata' is a directory on Windows. On a Mac, it is a 'package'. A package is a folder that looks like a single file and acts like a single file (you can double-click it to launch an application, for example). You can open the package (but you don't have to in this case) by right-clicking on it and then choosing 'Show Package Content'. Delete it as advised in that thread.

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The method for resolving the issue recommends deleting the Preview Cache directory which ends with Previews.LRDATA  but I'm not finding that. The closest thing I could find is a large (14gb) Previews.LRDATA file located in the Previous Catalogues folder, not an entire directory.

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MBP  M1,

Sonoma 14.5

By @cowbodyhat

This isn't a file. The Previews.LRDATA is the appropriate folder for the previews and should be deleted so LR has to rebuild the previews. In addition you should also delete the Smart Previews.LRDATA. It seems you're using Smartpreviews.