I used nothing but Linux for my Master’s and am currently using it for my doctorate. I’ve been full-time on Linux for over 10 years.
I did find that OnlyOffice played better with MS Office than LibreOffice. I also use the school’s Office 365 that they provided me to open my finished files in the web version to verify the formatting matched. There was only one time it didn’t.
The problem isn’t with Nextcloud (I had the same issue happen with me). The problem is with the default sync settings on Thunderbird and DAVx5 (at least for me). Thunderbird defaulted to a longer than I wanted synch schedule, so I dropped it down to syncing every 15 minutes. DAVx5 was set to 240 minutes unless the event was created on my phone. Once I updated both schedules to every 15 minutes, I haven’t noticed an issue.
OpenMediaVault (OMV) is a Debian server with a very user-friendly web interface. It also has solid documentation and a robust community. I’ve been running it for 6 years, and I am very happy with it.