Your LimeSurvey version: 3.x or 5.x
Own server or LimeSurvey hosting: Own installation
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Is there any alternative, configurable plugin for Limesurvey, who provide access to S3 cloud storage for upload type questions?

Haven't seen any public plugin for alternative storage for uploadquestions in years.
I cannot remember any feature request about that in the forum or bugtracker as well.
I recommend to submit a feature request.
Perhaps someone has done an internal modification to save files in S3.

Thanks for feedback!
I probably dig more on it in the next future. Then file a feature-request proposal or plugin development.