This is FYI only detail only sorry.
Ubuntu Studio 24.04 & 24.04.1 media installed the GA kernel stack (ie. 6.8 kernel), where 24.04.2 & later media installs the HWE kernel which updates; ie. it was 6.11 at 24.04.2, 6.14 at 24.04.3 and is 6.17 currently at 24.04.4 - it’ll upgrade next to 7.0 at 24.04.5 but that’s months away yet.
If interested; Ubuntu desktop flavors still follow the pattern of Ubuntu Desktop 18.04 LTS (and earlier) in the docs Kernel/LTSEnablementStack - Ubuntu Wiki
Switching to text terminal will allow you to use commands to explore what is going on, whilst this won’t help that much if you’re not familiar with POSIX standard commands; most OSes used today don’t stray too much from that standard anyway. (it will still feel alien to users who really only use mouse to point/click though)
I mentioned F4 as its what I usually used, no special reason, as the gap between F4 & F5 make it easy for me to find without needing to look.. so it wasn’t specific. On my current box I’ll use CtrlAltF2 to return back to my GUI, but even if you need to use F1 or F7 - you should find it easy enough.
As for shutting down; the Linux Kernel provides special keys that can be used to safely give commands bypassing any stuck/not-co-operating GUI (text or graphical), with those commands directly handled by the kernel (assuming they’re enabled and not disabled). It does require access to a keyboard on the device (not remote or using a on-screen-keyboard like most Android phone/tablets that are also using the Linux kernel). It’s a Linux feature; so we can use it down here on Ubuntu too.
SysRq was a key on IBM PCs, XTs, ATs, PS/2 etc.. It wasn’t a specific key, but was a special purpose secondary-function and had the SysRq printed on the front of the key in a color (not black like most printing on keyboards). Modern keyboards are often thin and don’t have the space at the front for what used to be printed on them (not printing also reduces cost), so its common for modern devices to not have it marked. Whilst some brands actually mentioned the key in their documentation when it no longer printed (ie. key combination that achieved it), even that disappeared as documentation was reduced & devices changed more often. To find the key, looking at an older keyboard (either in picture, search online) should provide clues on where it will be on a newer device without it marked (its always worked for me anyway; but I also use old IBM Model M keyboards anyway so use keyboards that have it marked).
On some newer devices it can be harder to use, as they mandate me adding an extra key (Fn) to achieve the SysRq function of a key (as PrintScreen|ScrollLock|Pause/Break keys got re-purposed as media keys etc which are more useful to most users), but that’s what I meant with SysRq - it’s a key on an IBM compatible DOS/Windows computer; alas hard to find on smaller consumer devices or any device post-2021 but it’s still there.
As for using it; if I needed a doc; I’d probably pull out a phone and search “magic sysrq” and expect to find the Wikipedia page near the top of results; that is good enough to remind or work out keys. The common commands (like REISUB) are usually used as examples in docs anyway.
At text terminal you’ll get messages appear if you’re using a kernel with keys disabled (you’ll see nothing if using a graphical interface to your machine), where on my current resolute (26.04) system I get told it’s disabled when I hit R, E or I, but I get told the S or Sync command was executed (I stop there; as I’m not running subsequent commands on this working system!). Each letter represents a command; eg. B = reBoot, which could be replaced by O = Off; a super quick way that I use on occasion to shutdown a system because I really have to go in a hurry.
SysRq commands allow you to [somewhat] safely do things, which are far less potentially destructive as using a power-button and forcing the system to uncleanly shutdown. Using commands I can tell the system to shutdown safely using commands (eg. S is the command to sync/flush buffers & ensure everything needed is written to disk); power off button could leave disk in an unknown state or problems due to data still being in RAM that never got saved to disk; data in RAM being lost when power went off.
