To select a choice referencing a csv file, you are have to copy some fields in your survey datasheet (choices or external_choices).
Would it be possible to use an external reference file (e.g.: sqlite, other) to populate a select list and make it fast ? (ref. https://community.esri.com/ideas/16568-use-pulldata-feature-to-populate-selectone-choices - only with a better perfoming technical solution than CSV files)
Today I don't see how to use a huge reference list (e.g. 100k + lines floristic or faunistic data) in a Survey123 form. Our tests using choices/external choices result in ~8 to10 second survey loading time for 4000 lines only(!).