Consider implementing an alternative to selectize.js #4227
Description
Shiny's selectInput() (when selectize = TRUE, which is the default) and selectizeInput() depend on the selectize.js javascript library, modified by a number of bespoke patches contained within this repo. Unfortunately, selectize.js doesn't appear to be actively maintained. One of its last maintainers, who says he doesn't even have the perms to cut a release, just created a thread to discuss how to best direct people to alternatives: selectize/selectize.js#2205 This means that any of the various issues with selectize in shiny that are downstream of bugs in selectize.js, are unlikely to ever be fixed without further difficult-to-maintain custom patches.
Therefore, it may be worth considering implementing searchable-select input in shiny via a different, actively-maintained javascript library. The linked thread above suggests a few possible alternatives, including Tom Select (a fork of selectize that miiiight be workable as a drop-in replacement). I'm not sure whether it would be possible to smoothly swap out the underlying JS library, or if the functionality would need to be recreated from scratch with a new corresponding shiny input type.