"Curiously", Nextcloud aimed at one of the main competitor of its product - and that running on a desktop OS - ignoring Dropbox, Google Drive, iCloud, etc. Probably because they are interested in the office space.
Also it's funny how Germans like to protect their pharma, chemical and other sectors intellectual properties very hard ("open sourcing" Covid vaccines? NEVER!!!!!) but are very keen on exploiting software open source, since they could never create a thriving software industry in Germany beyond SAP and little else, to avoid to invest there really.
I'm very favourable to open competition, and software licensing prices must allow it - but it can't be an excuse to bend the market from favouring one side to the other. I'm also very favourable to open standards (as in a remote storage protocol) for iteroperabilty, far less in forcing everybody to open their code - which is actually greatly helping the cloud Goliaths to exploit smaller companies.
"Digital sovereignty" then is another matter than needs to be regulated accordingly to citizens' rights, especially since bad laws like the CLOUD Act stand, and companies outside EU can't really safeguard citizens' data as GDPR requires, no matter how many "safe harbours" or "privacy shields" they can devise, unless the other state laws don't provide the same level of protection.