I haven't seen any examples of Survey123 being used to crowdsource information from the public. I know you can do this with GeoForms but their survey format seems a little limited. Thanks!
Yes it is possible to make a Survey123 survey public and this will enable users to submit data anonymously (no login required) - this works via the field app or web app. Please see: Share survey—Survey123 for ArcGIS | ArcGIS
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