Struggling to fix things changed by the ‘upgrade’ to Cinnamon 6.6, but unable to find how to reconfigure the Compose key which was completely wiped out. 
And turn off Caps Lock!
The System Settings > Keyboard > Layouts has apparently lost the ability to make those keyboard modifications.
same an upgrade available from 6.6.0 to 6.6.2 and installed with hope
didn’t work
This is a deal-breaker. If I can’t get this fixed, more than a decade of using Cinnamon will come to an end.
Confirmed, also all of the option settings seem to have vanished. 
Albeit running on X11, it has also added an env var
QT_IM_MODULES=wayland;ibus
(note plural; ibus is my selected IM for GTk & Qt).
For the time being, I can (and have to) reset my options using setxkbmap manually each login like so:
setxkbmap -option "lv5:lsgt_switch,compose:caps,keypad:future,nbsp:level2,terminate:ctrl_alt_bksp,grp:win_space_toggle"
Can’t remember all the stuff I fixed in week-long sessions until my keyboard was set up perfectly for my needs, or how to make it permanent (apart from using the GUI, which went). I simply hate it when an update messes with my fine-tuned settings for the keyboard, developed over many years! That was one of the reasons I left Windows 13+ years ago—the “I know it better than you anyway and shit on your settings” approach. Grmbl.
If I selected X11 over Wayland in the first place, there was a reason! If I declare my IM to be ibus I want ibus, and if I decide to use a slightly modified German E2 layout, I probably need that as well, DAMMIT. And not whatever some idiot has declared a nice default.
Completely agree. If this doesn’t get fixed soon, I’ll be switching to MATE.
I’d actually prefer to keep Cinnamon, been a trusted friend over decades now. But at least we know that at least underneath good old X11 still does its job as well as it ever did…
Would hate when they now all started removing features we built and waited for oh so many years, just to “stay in line” with a totally over-hyped Wayland, “just because all the others do it too.”
Sure, throwing features outta the window that the average Joe seldom uses makes things simpler, shinier and seemingly finished earlier. Not Linux-ish anymore, though. And the next display server/compositor will eventually go down the same drain and get patched & extended over and over again, just to re-add the same features again, because just some professionals do actually need them. Only those will suffer for years until things are usable again.
And yes, sometimes it’s just a few foreign letters, or compose table entries. That’s what we love Linux being able to do.
LLAP 
some of the problems can be fixed with the dconf editor
In
/org/cinnamon/desktop/input-sources/xkb-options
turn off ‘Use default value’ and make entries in ‘Custom value’ between the brackets.
I tried [‘ctrl:nocaps’] ← that worked
[‘ctrl:nocaps’, ‘compose:rwin’] ← that did not work for the Compose key, Cinnamon ignored it
[‘ctrl:nocaps’, ‘compose:ralt’] ← not the key I usually use as the Compose key, but it gives me a Compose key
I’ve not yet figured out a way to configure a key combination to switch between keyboard layouts.
Well, I guess this has nothing to do with a hype. A hype is more like a sudden interest and adoption of a new technology, e.g. AI, blockchain, virtual reality, etc. But wayland is far from being a hype. It is just too old. Wayland started in 2008. Gnome started to use wayland in 2016. Now in 2025 several desktop environments have announced that they will go all in to 100 % and stop support X11.
Wayland is the future. Ignoring it is not the solution. Supporting it is not a hype but a necessity.
The bug has been assigned for a fix.
Upgraded to Cinnamon 6.6.2, but problem is not fixed.