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SurveyJS
Open-Source JSON Form Builder to Create Dynamic Forms Right in Your App. With SurveyJS form UI libraries, you can build and style forms in a fully-integrated drag & drop form builder, render them in your JS app, and store form submission data in any backend, inc. PHP, ASP.NET Core, and Node.js.
Maybe Mistborn (https://gitlab.com/cyber5k/mistborn) could work? It has Rocket Chat and Jitsi available as well as a number of other features.
And, a full options web client is Movim (text, files and video). Regarding security, OMEMO is available on Ejabberd, Conversations, Converse.js and Movim. Jitsi-meet encrypts 1 to 1 communications for sure, you might dig up for many-to-many encryption.
If you haven't checked out Trnago - I recommend taking a look at it for network only video, voice, chat, etc. https://github.com/trango-io/trango-self-hosted