The article 'dat' doesn't match with Nordic languages. Google translate says its Krio language, which is English-based and lingua franca in Sierra-Leone. However, I can't tell whether that's correct.
There are two specific problems I see here for the mentioned binaries.
The software is packaged as a generic archive, no format like rpm or deb the system package manager could/does handle. Thus, the package manager of your system does neither know that you've installed this binary nor what it depends on. The developer could have at least mentioned on which exact system the Linux binaries are supposed to work, e.g. Ubuntu 22.04, so that the user knows, that they might have issues running it on a different system.
The developer could have built and packed it in a way that it can be installed by the package manager of a specific distribution. Launchpad or OBS are made for this purpose. The other option, wrapping it as a flatpak, works too, but may bloat the system of the user as different versions of the same libraries are installed (system generic + flatpak version).
Nonetheless, as a Linux user, you are encouraged to build directly from source.
When I had the issue with mariadb demon been killed, I think either in dmesg or syslog there was an entry reading "Out of memory: Kill process... " or similar.
In principle any DAV client should work. On Android, I use DAVx5 and Tasks.org to access my Nextcloud. On Thunderbird + Lightning, you can e.g. use SOGo connector or TbSync to use the address books, calendars and tasks.
I don't know about Fedora, but Debian keeps at least the previous version. However, that's about it. There remain only 4 (2 normal + 2 recovery) GRUB entries and the additional ones vanish automatically during the uninstallation procedure.
I wouldn't recommend it for a noob, but the setup process isn't too complicated either. Its benefit is definitely its stability and long update period, the downside is that some software might be a bit outdated, but today, however, one can get fresh versions, of e.g. Inkscape or GIMP, as flatpak.
What you guys are referring to as Linux, is in fact, GNU/Linux, or as I've recently taken to calling it, GNU plus Linux. Linux is not an operating system unto itself, but rather another free component of a fully functioning GNU system made useful by the GNU corelibs, shell utilities and vital system components comprising a full OS as defined by POSIX.
Many computer users run a modified version of the GNU system every day, without realizing it. Through a peculiar turn of events, the version of GNU which is widely used today is often called "Linux", and many of its users are not aware that it is basically the GNU system, developed by the GNU Project.
There really is a Linux, and these people are using it, but it is just a part of the system they use. Linux is the kernel: the program in the system that allocates the machine's resources to the other programs that you run. The kernel is an essential part of an operating system, but useless by itself; it can only function in the context of a complete operating system. Linux is normally used in combination with the GNU operating system: the whole system is basically GNU with Linux added, or GNU/Linux. All the so-called "Linux" distributions are really distributions of GNU/Linux.
The most obvious difference for the end-user compared to Windows is that you can choose different desktop environments, such as KDE, GNOME, XFCE, LXQt, Mate or Cinnamon to name the most prominent among others.
As you are used to the look-and-feel of Windows, I'd suggest giving KDE a try.
For a beginner, I'd recommend using a 'beginner friendly' distribution such as Kubuntu (Ubuntu with KDE) or Linux Mint (based on Ubuntu using Mate/Cinnamon DE). Fedora, Linux Mint Debian Edition or plain Debian are also suitable, but for a more experienced user.
If you are interested in editing text files as root directly from nautilus, the package nautilus-admin may be helpful. Link
As I am using KDE, I know that Kate, the KDE text editor, prompts for the sudo password when saving an edited text files that is owned by root. I don't know if Gedit does the same.
The article 'dat' doesn't match with Nordic languages. Google translate says its Krio language, which is English-based and lingua franca in Sierra-Leone. However, I can't tell whether that's correct.