Windows LR doesn't correctly open a catalog folder exported with Mac LR with File > Export As Catalog, Export Negative Files, if the Mac catalog folder contains subfolders with non-ASCII characters (e.g. á or é).
To reproduce on LR 14.2 / Mac OS 15.2, Windows 11:
1. Download this .zip file containing a catalog and photos to your Mac desktop:
https://www.dropbox.com/scl/fi/stbx8iyfekqk9xkuri3fi/accents.2025-02-14.zip?rlkey=xt283tc32rjarroeu4...
It contains a catalog created with Mac LR by doing FIle > Export As Catalog, Export Negative Files.
2. Unzip and open that catalog in Mac LR. Observe that it contains four photos in two folders and none of the folders or photos are marked missing:

2. Download the .zip file to your Windows desktop.
3. Unzip the .zip using these exact commands:
cd Desktop
tar xfzv accents.2025-02-14.zip
Do not use the Windows ZIP built-in to File Explorer. It still doesn't correctly handle paths containing UTF-8 characters (hey, it's only 2025).
4. In Windows File Explorer, verify that the extracted catalog folder "accents" has this structure, the same as in the original catalog folder on Mac:
accents
accents.lrcat
pics
a
e.jpg
é.jpg
á
e.jpg
é.jpg
5. Open the "accents" catalog.
6. Click on All Photographs and observe that all four photos and the three folders are marked as missing (incorrect):

7. In the Folders panel, click on "pics" and observe that "pics" and "a" are no longer marked as missing, while three of the photos are missing and one is not (all incorrect):

8. Click on All Photographs, and observe that "pics" and "a" are marked as missing again. You may have to adjust the thumbnail size larger or smaller a few times until that happens. The erratic behavior here clearly shows LR is confused.
9. Right-click on "pics" and do Find Missing Folder. Navigate to Desktop\accents\pics. Observe that "pics" and "a" are no longer marked missing (correct) but "á" is still marked missing (incorrect). Observe that the photos in "a" are no longer missing (correct):

10. Right-click on "á" and do Find Missing Folder. Navigate to Desktop\accents\pics\á. Observe that "á" and its two photos are no longer marked missing (correct):
