Please help us help you and fill where relevant:
Your LimeSurvey version: [5.6.32+230731]
Own server or LimeSurvey hosting: CE, own server
Survey theme/template: fruity
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I have just upgraded to the newest version, access a running survey, click on the "survey participants" field, click "display participants" and that was it: the browser (Firefox, same in Edge) is waiting, nothing happens anymore. What can I do?

Yes, it's a known issue.
[url] forums.limesurvey.org/index.php/forum/ge...ohne-funktion#245507 [/url]
And seems to be fixed already.
[url] github.com/LimeSurvey/LimeSurvey/pull/3323 [/url]

The fix was provided today by Comfort Update, too.