Ocis/OpenCloud can integrate with Collabora, OnlyOffice but don’t currently have things like CalDAV, CardDAV, E2EE, Forms, Kanban boards, or other extensible features installable as plugins in Nextcloud.
If you desire a snappy and responsive cloud storage experience and don’t particularly need those things integrated into your cloud storage service, then Ocis or OpenCloud might be something to look into.
Given the Linux initramfs targets a block device as a file that then gets mounted as the persistent root filesystem, I don’t think it would really be possible to unmount / and replace the location with a file. Root isn’t represented as a file or directory in any filesystem structure and is a construct of many Unix and Unix-like kernels.
Certainly a failure but at least it wouldn’t actually be as harmful as it reads, given / is a directory and the assumption you’re not root.
In order to maintain software versions, package maintainers will often selectively pull git commits from the upstream projects that fix bugs / vulnerabilities in the code, while not pulling feature commits. Sometimes the pulled commits may need modifications to work properly on an old feature version of the software, which will also be done during the process. Alternatively, a software may be compiled with different feature flags to restrict functionality to mitigate bugs known in upstream.