Hello,
Thanks for reaching out! Hmmm, the buttons should be navigable with a tab via a keyboard. In this short video here using the Buttonizer site as an example, I was tabbing and skipped the first menu button for ChatGPT assistant and went to the second one and clicked it via the enter key. Then I navigated through the sub-menu buttons and clicked the YouTube tutorials button all via keyboard. You can see the URL change in the bottom left as they are being tabbed through.
Hope that helps! Please let me know if you were referring to something different of course.