Video thumbnails stopped working within gocryptfs mounts after updating to KDE frameworks 6.1

Description:

Previously with ffmpegthumbs installed, I was able to see thumbnails for all supported video files on my various disks in Dolphin. However, after I did a system update today which updated all KDE frameworks related packages to 6.1, I noticed that the videos within my plasma vault (which is backed by gocryptfs) are no longer showing thumbnails. Video files on other filesystems are not affected.

Things I've tried:

• Reboot. No change in behaviour.
• Reinstalling ffmpegthumbs. No change in behaviour.
• Create a symlink on a "regular" file system to the video within gocryptfs. Thumbnail does not show.
• Copy the video within gocryptfs to a "regular" file system. Thumbnail shows correctly.
• Create a symlink within gocryptfs to a video on a "regular" file system. Thumbnail shows correctly.
• Launch Dolphin from a terminal. No noteworthy logs.

Additional info:

• package version(s):
  • ffmpegthumbs: 24.02.2-1
  • dolphin: 24.02.2-1
  • frameworkintegration: 6.1.0-1
  • kernel: 6.8.5.arch1-1

Steps to reproduce:

1. Prepare a video file, MP4 or anything that's supported.
2. Observe that in a "normal" file system like exfat, ext4, or btrfs, Dolphin shows the video thumbnail correctly.
3. Create a plasma vault backed by gocryptfs, and copy the video file into it.
4. Observe that Dolphin does not show the thumbnail of this video file.
5. If possible, find a machine that is still on KDE frameworks 6.0. Observe that this problem does not exist.