Re: Cloud Act?
To what extent would we want alternatives to major cloud providers? As things stand there must be few clients who are not rounding errors in the bottom line of their US service providers.
As far as stuff like OneBox or whatever it's called is concerned, NextC|loud with the desktop client installed does the job fine, is based on open standards and provides for calendar sync and a number of collaboration tools. There are plenty of EU & UK suppliers who will run it for you if you don't want to run it in-house.
Likewise there are EU and UK suppliers who will host email.
For "major" read "many".
The bits needed to make up Microsoft <365 of the Google equivalent are there.but there is scope for some integration work, the sort of thing that the Microsoft ID handles. There's also scope for a ChromeOS equivalent which will integrate with the users' choice of service provider including an in-house server if preferred. It's those areas where I would see the efforts of a "Collective" being best applied.