A Microsoft file hosting and synchronization service.
During the process I explained above, those folders went from having the little check mark beside them, which indicates they are syncing with OneDrive(like the rest of those folders pictured), to having the cloud icon beside them.
Cloud files are always in sync with OneDrive. When you open a cloud file it downloads to your device and becomes a locally available file. Then you can make changes to the file. So with regards to syncing, it doesn't matter what type of icon the file has in your local OneDrive folder.
Previously they were not "cloud only"! So something happened that made them "cloud only".
This could be due to Storage Sense freeing up space automatically. So check those settings.
Quoting the article:
Manage locally available cloud content
To choose the conditions for when inactive files are made online only, under****
***Content will become online-only if not opened for more than:***choose your preferred amount of time.
Note that starting in Windows 11, version 22H2, the default for OneDrive cloud files is to make files online-only if not opened for more than 30 days."
If I do what you are prescribing it will change the icon to a solid green circle with a white check mark inside, which means that it won't sync with OneDrive?
No, that is not the case. When OneDrive is running, all files in the local OneDrive folder always sync to OneDrive regardless of the type of icon they have.
Check this out: https://support.microsoft.com/en-au/office/what-do-the-onedrive-icons-mean-11143026-8000-44f8-aaa9-67c985aa49b3