At some point leading up to Drupal 8.9, collapsible fieldsets lost their collapse/expand icons in the Seven theme.
For example, here are two pages that have collapsible fieldsets in Drupal 8.9.13:
I wish I could get SimplyTest.me to load-up older versions of Drupal 8, but it's failing at the moment. But, in the screenshots above, all the fieldsets should have triangle icons like this:
Visit any page that has collapsible fieldsets (e.g. update.php, regional settings, performance settings, etc).
Locate the change that caused these icons to go missing and revert it.
Restore missing collapsible fieldset icons in the Seven theme.
Postponed: needs info
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
#17
Yep, noticed it too.
The simplest workaround I use for now is just to copy
web/core/misc/logo/ and web/core/misc/icons/ to web/themes/misc/
Changing the paths would be smarter way, but I am just a lazy guy.
It seems this has been already fixed in 🐛 Icons are missing Fixed .