OpenDesk by the Centre for Digital Sovereignty

For people looking for community edition and how it can by used by anyone, here [1] you can find it

[1] https://gitlab.opencode.de/bmi/opendesk/deployment/opendesk

A public demo or some screenshots would go a long way, imo. Even finding the comunity editiion took me a minute...

how does it compare with nextcloud?

This actually uses nextcloud for its "File Storage" component. It's not a from-scratch system but a bunch of existing pieces of software all packaged together.

I think this can work well but it really really depends on if the components are chosen well and integrated with each other well.