Hi, please check this conversation: https://community.adobe.com/t5/adobe-xd-discussions/get-ui-kits-webpage-gives-error-404-in-xd-55-2-v...
Pasting @HARSHIKA_VERMA 's answer:
We are aware that Get Ui kits are currently routing you to this help article: Access UI kits, plugins and app integrations where you are unable to download the UI Kits as the downloadable file links are not available on the page.
Please check this page for now: What Is a UI Kit? Examples & How to Use | Adobe XD Ideas, which might help you with the famous UI kits.
The team is working on adding the kits to the page and we will share the updates with you as soon as it's done.
We are sorry for the inconvenience.
There are also UI kits at https://www.xdguru.com/free-xd-ui-kits/
Hope this helps!
I am delighted to inform you that the UI Kits help page issue has been resolved. The UI kits are available here: Access UI kits, plugins and app integrations.
Please accept our sincere thanks for your patience as we tried to solve the issue. We sincerely appreciate your patience and assistance.