With regards to security, nothing is perfect but I'm absolutely positive that Nextcloud is ahead of the vast majority of open source projects. And if you know of a security hole, go and collect your USD 10K at HackerOne.
True. I don't know of any other "holistic" project that we could have choosen instead of Nextcloud. One very very important point is the AIO installation method. So easy and no fear to have forgotten something important. -- You saved us from Google (no way) and Microsoft365 (a possibility), thank you!
With regards to security, nothing is perfect but I'm absolutely positive that Nextcloud is ahead of the vast majority of open source projects. And if you know of a security hole, go and collect your USD 10K at HackerOne.