Reactified components TagsSelector and TagsBox not showing tooltips

I am working on a bootstrapped plugin and I'm trying to stay away from XUL as much as possible, using HTML/React instead.
I'm trying to add some tooltips for some buttons and icons, but using the "title" attribute doesn't seem to work.
Based on the reactified parts of the Zotero code (see [1] and [2]), I tried using the XUL attribute "tooltiptext" as a workaround, but it doesn't seem to work either.
In fact, I'm not seeing the tooltips for these native reactified components either. I'm using version 5.0.94 and I expected an "Actions" tooltip to appear on the #tag-selector-actions button of the Tags Selector, or a "User-added tag" tooltip on the icon to the left of a user defined tag in the Tags Box, but neither appear. I'm using Linux Mint 19.2, by the way.
Is this a known bug? Thanks!!

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