showPopover seems to be a fairly recent api, available in Firefox releases after April. Not untypical that e.g. Debian releases, are a bit behind, iirc.
It can most likely easily be fixed by adding a polyfill (https://github.com/oddbird/popover-polyfill).
Although it is nice to use recent js APIs, I think it would be beneficial to support some later versions of browsers. At least be very clear about what you support. Ideally telling users when they are on unsupported browsers/versions.
https://caniuse.com/mdn-api_htmlelement_showpopover
I would expect older iOS devices to struggle with this as well. And not all iOS users can upgrade.
I guess assistant is relying a lot on client side js, while search is not. I’ve seen several threads on similar problems.
