***
After snap refresh to okular snap 25.04.2 today, okular is unable to start up due to:
"/snap/okular/171/usr/bin/okular: /snap/okular/171/kf6/usr/lib/x86_64-linux-gnu/libQt6Core.so.6: version `Qt_6.9' not found (required by /snap/okular/171/usr/bin/okular)"
***

SUMMARY
Refresh of okular snap to 25.04.2 2025-06-11:
$snap info okular
...
snap-id:      SfUqQ280Y4bJ0k64qtBKTTXq5ml46tvQ
tracking:     latest/stable
refresh-date: today at 18:23 CEST
channels:
  latest/stable:    25.04.2 2025-06-12 (171) 72MB -
  latest/candidate: ↑                             
  latest/beta:      ↑                             
  latest/edge:      25.04.2 2025-06-11 (171) 72MB -
...

fails to startup due to missing Qt_6.9 version:
"/snap/okular/171/usr/bin/okular: /snap/okular/171/kf6/usr/lib/x86_64-linux-gnu/libQt6Core.so.6: version `Qt_6.9' not found (required by /snap/okular/171/usr/bin/okular)"

Revision to 170 results in working version.
STEPS TO REPRODUCE
1. snap refresh okular 
2. start okular

OBSERVED RESULT
Failure to startup

EXPECTED RESULT
Working snap of okular

SOFTWARE/OS VERSIONS
Linux: Ubuntu 22.04
snap    2.68.4
snapd   2.68.4
series  16
ubuntu  22.04
kernel  6.8.0-60-generic

ADDITIONAL INFORMATION
Revision to 170 / 25.04.1 restores working version:
"snap install okular --revision 170"