dpkg --list | grep linux-image
Find the remaining kernel, then sudo apt remove... any above 5.8
dpkg --list | grep linux-headers
Same as above
dpkg --list | grep linux-modules
Same as above... Once you have cleaned out all remaining pieces of 5.11, please reboot and test.
(I guess you could also do the same in Synaptic - by searching for 5.11.0-38, selecting any as "remove completely" and then clicking apply.
It just now occurred to me. I use the terminal for most things.)
Well this is bizarre; after listing and removing all those components Terminal now reports that I'm running the 5.8.0-63 version on boot up but the sleep > wake issue has returned.
I tested it numerous times using both the power button (set to sleep) and closing the lid + walking away and it worked when I had to select which kernel to run 
It was a short lived success... but a sweet one. I will always remember it...
Indeed. I will treasure the memory 
Should I try putting back in 5.11.0-38 and see if that makes any difference?
You could, just to see if it duplicates the Suddenly working when selecting the kernel or not...
Other than that, my brain blew a fuse. I will try researching the issue a bit.
If you thought that was bad; I just put 5.11.0-38 back in and low and behold the sleep function is working correctly again when you select to boot from 5.8.0-63 on grub
It acts as though there is a cross dependency; which makes no sense to me lol
Agreed, it doesn't.
Let's set grub to boot from the last Kernel you selected. Boot into 5.8, then open a terminal and
sudo nano /etc/default/grub
Change GRUB_DEFAULT=0 to GRUB_DEFAULT=saved
Then hit enter to make a new line and add this line into that space: GRUB_SAVEDEFAULT=true
Hit ctrl+x to exit, then the y key to say yes to save, then the enter key to save as current configuration.
The terminal will revert to normal- run sudo update-grub
Then reboot and test...
Okay I've got another log of 'that's weird' to add to the pile of 'why the heck is that happening'
I made the changes to grub and updated it. Rebooted the machine and selected the 5.8 kernel under advanced. Verified it was running 5.8. Tested the Sleep > Wake (multiple times) and everything was fine.
Powered off and Powered on the device. Let the timer run out so that the system would automatically boot the default selection in GRUB. Verified that the version running was 5.8. Tested Sleep > Wake. 1st time it worked. 2nd time it woke up then immediately went back to sleep so I woke it again. 4th time it went to sleep and never woke up.
Powered off and manually selected 5.8. Retested Sleep > Wake multiple times. No problem.
You may need to tell your girlfriend to get used to booting from Advanced Options and double check your pre-nup.
LOL.
Well the good news is it also seems to work if, on bootup, you leave the selection (which is already on Advanced) alone and just keep pressing enter (5.8 gets selected automatically). So as a workaround it isn't terrible but I do hope this gets addressed.
Since 5.8 is being selected now should I leave those synaptic files locked? Or is it better to let the system update things and just let Grub select the 5.8 on bootup?
Spoke too soon again!
LOL! So it also seems there is a difference between closing the lid and pushing the button (set to sleep). If I push the button after 1-2 more sleep > wake tests everything locks up and the system stops waking.
What does running:
gsettings get org.gnome.settings-daemon.plugins.power button-suspend
In terminal yield?
It responded with 'suspend'
Which is what it should... Given your "spoke too soon" post above, thought we were onto something there.
No lead, after-all.
Well we are onto something. What I'm finding is, having turned off the option in settings to sleep from power button, that closing and reopening the lid is consistently working.
I don't know why closing the lid would be different from pressing the 'sleep' button but this is at least a viable option for the time being.
If you have any scenarios you want me to try specifically please let me know and I'll test them out.
This sounds like a viable work-around to me.
For sure, it works for now and should be easy for the girlfriend 
Hopefully this can be addressed in a future release
Thanks again for your help.
When the system freeze can you do alt + f2 ? When a terminal pops up write r and hit enter.
Tried this after the computer locked up again (more on that later) and the keyboard/mouse do not register at all. Nothing comes up with that keyboard combination alt + f2
So I had to switch back to the windows installation on the laptop today to open a file for the girlfriend. After switching back to the 5.8 kernel the machine started locking up again.
I finally got it back to the point where sleep mode works by doing the following:
any other combination or switching to windows and the computer would lock up at sleep.
Very bizarre behaviour. Wondering if there is another kernel I should try?