A crash in the window manager takes down all running applications: Yes, because the compositor IS the server, window manager AND compositor at the same time.
Maybe not anymore in the future: https://blog.davidedmundson.co.uk/blog/qt6_wayland_robustness/
Wayland is biased towards Linux and breaks BSD
FreeBSD already has working Wayland compositors by the way.
X11 and Wayland are just protocols. These protocols are used to abstract the window drawing from the actual hardware and runtime environment as much as reasonably possible - because nobody wants to maintain 3215 versions of their app for different runtime environments. So in order to be shown on the screen an app needs to implement either the X11 or the Wayland protocol (or both!).
The piece of software that is on the other side depends on whether the app is using X11 or Wayland. For the sake of simplicity let's assume that the app does only support one of those. If the app supports Wayland then it will try to connect to a Wayland compositor. The compositor implements every part of the protocol and makes sure that the window is rendered on the screen and that user input is forwarded to the app. If the app supports X11 then it will try to connect to a X server and take the role of an X client. This is (on Linux, essentially) always X.org*. X.org also implements every part of the protocol and makes sure that the window is rendered on the screen and that user input is forwarded to the app.
* Unless you're running a Wayland compositor, then it will connect to XWayland which passes through the window to your compositor.
Wayland compositors have full control over the apps while the abilities of apps are purposefully restricted.
A window manager is just another regular, boring, old X client connecting to the X server. It doesn't actually abstract anything. It can move windows because the X11 protocol allows it to, but any other X client could just as well move all other windows around, read all user input to all other windows and even move the mouse around as it pleases.
So, to be specific, there is no mouse pointer bug in Virtualbox while using Wayland. There is a mouse pointer bug affecting specific Wayland compositors, likely because they enforce GPU hardware acceleration that is lacking in either your VM or the Linux kernel because of missing drivers. Try using a different compositor, (re)installing Virtualbox Guest Additions with the correct version on the guest system and/or check whether hardware acceleration is enabled for the VM and has enough video memory.
Thank you for explaining what Wayland really is: a protocol. I see way too many people in forums going "Wayland constantly crashes" or "this doesn't work with Wayland" but what they actually mean is that their compositor of choice crashes or lacks a feature. There are a few things that Wayland doesn't support (like multiple-main-window-apps that want to put their children relative to each other (i.e. multi-window Gimp)), but that's usually not what's being discussed.
But please allow me to correct you on a few details:
X is commonly available as a shortcut to start the main X server installation though.far more efficient than with X11
In theory. The issue is that, at this point in time, the vast majority of software that actually needs this efficiency (read: video games) run on XWayland, which adds a bit of overhead which ultimately causes them to run slightly slower on Wayland compositors compared to X.org. Maybe this will change at some point as devs patch their native games to check for a Wayland compositor by default and the big set of Wayland-support-patches makes its way into wine (and hopefully proton).
X12 actually exists. That said, it never went further than an extremely rough draft and was abandoned at some point, ultimately in favor of Wayland.
I don't know about the creators of this project, but in general: So that they can use the stuff in their closed source applications while finding enough contributors to write software for them for free.
Have a separate home partition and just keep using it across distributions?
So that people can't easily track how much time is spent on getting round window corners compared to how much time is spent not implementing thumbnails in a file chooser dialog?
18 years, by the way.
Screwed up fonts in GTK software, even though the xdg-portal app for KDE is installed. At some point I just gave up. I see no reason to install any Flatpak if the software in question is already in the distro's repository and current enough anyway. Maybe except OBS, because the Flatpak version comes with Youtube integration which, to my understanding, needs to remain closed source and won't make it into a FOSS repository.
Do you mount the drives using their /dev/sdX entries or via UUID? Because it sounds like you're using /dev/sdX entries (which you really shouldn't, because their names can randomly change, by design). Use /dev/disk/by-id/... directly for mounting or, alternatively, fill /etc/zfs/vdev_id.conf (see example below) and define the pool using their aliases.
´alias Bay1 /dev/disk/by-id/ata-XXXXXXXXXXX1-YYYYY1_ZZZZZZZ4
alias Bay2 /dev/disk/by-id/ata-XXXXXXXXXXX2-YYYYY2_ZZZZZZZ4
alias Bay3 /dev/disk/by-id/ata-XXXXXXXXXXX3-YYYYY3_ZZZZZZZ4
alias Bay4 /dev/disk/by-id/ata-XXXXXXXXXXX4-YYYYY3_ZZZZZZZ4`
I hope Microsoft will never go with the subscription based OS approach that is being rumored about. I seriously can't afford that much popcorn.
That's my personal experience, as well.
That something entirely different than the protocol being biased towards Linux. It's like complaining that TCP/IP is biased towards Linux because the Linux kernel's networking module can't be used in BSD kernels.