Steps to reproduce the issue

1. Enable content page navigation plugin for your blog (is default)
2. Oben an article in a blog (in Cassiopeia)
3. See the navigation Button(s), set the focus on one of them

Expected result

Navigation Buttons show a visible focus ring when they get the focus.

Actual result

No focus border.

Device and system info

• What version of Joomla were you using?
  4.1

• What device were you using? (eg, phone, laptop)
  laptop

• What web browser were you using? (eg, Chrome, Safari)
  Chrome, Firefox

• If you were using assistive technology, please let us know the device or software you were using (eg VoiceOver, JAWS, sip-and-puff device, etc)

Additional comments

If you know which WCAG or ATAG criteria this violates, please indicate it here:
https://www.w3.org/WAI/WCAG21/Understanding/focus-visible.html