Hi @RaffyM and welcome in the ODK community
Yes you can do something close to autocomplete search.
Because select-widget-with-autocomplete will not be able to work in such a big list you will have to use the search() function.
But its documentation page needs to be completed
See this discussion :
Here you can see how we use it to collect species data : ODK to collect species and habitats localities, as pressure and threats to ecosystems
I just edit the showcase to complete the part relative to this.