UK Home Office Design System Accessibility Standards - https://design.homeoffice.gov.uk/accessibility/standard
German Government Accessibility Standards - https://webtest.bitv-test.de/index.php?a=dl&t=s
US Government Accessibility Testing Approach Guidelines - https://section508coordinators.github.io/TrustedTester/
Swedish Government - https://trg.digg.se/manual/
Latvian Government - https://pieklustamiba.varam.gov.lv/
Microsoft Accessibility Insights - https://accessibilityinsights.io/
IBM Accessibility Requirements - https://www.ibm.com/able/requirements/requirements/
Orange Digital Accessibility Guidelines - https://a11y-guidelines.orange.com/en/
W3C Accessibility Checkpoint Master List - https://www.w3.org/WAI/EO/wiki/Accessibility_Checkpoint_Master_List
AInspector Sidebar - https://ainspector.github.io/
(List based on a xGov Slack thread started by CDDO's Anika Henke)