I see improvements to the btrfs-overlayfs hooks, but it doesn’t seem to have been modified for the systemd variant.
~
❯ grep "^HOOKS" /etc/mkinitcpio.conf
HOOKS=(base udev autodetect microcode kms modconf block keyboard keymap consolefont plymouth filesystems)
found a mkinitcpio.conf.pacnew file in /etc - which was also mentioned during pacman -Syu. It included the systemd and sd-vconsole hook.
after some reading i modified my hooks to systemd instead of udev and sd-vconsole instead of keymap and consolefont. see mkinitcpio - ArchWiki
(not sure why the pacnew had keymap and sd-vconsole. keymap should not be needed when sd-vconsole is used)
the btrfs-overlayfs hook was found in
/etc/mkinitcpio.conf.d/10-limine-snapper-sync.conf
I manually modified it to use the sd-btrfs-overlayfs variant :
❯ cat /etc/mkinitcpio.conf.d/10-limine-snapper-sync.conf
# This hook is necessary for the proper loading of Limine snapshots.
# Please do not touch unless you know what you are doing.
HOOKS+=(sd-btrfs-overlayfs)
since i use limine I ran
sudo limine-update
which also regenerates the initramfs images
Just to be sure I installed a Cachy into a vm with the setting I use on my Framework (Limine, BTRFS with encryption). I used exactly those settings for the HOOKS in mkinitcpio.conf and changed the sd-btrfs-overlayfs. But the system could not boot.
Did not even show the promt to enter the encryption-password.
Snapshots saved my ass, as I could restore the last one.
smart move 
did you include the sd-encrypt hook for encryption support?
And put keyboard before autodetect.
See table 3.3.4 Common hooks in mkinitcpio - ArchWiki
Yes, I used this HOOKS:
HOOKS=(base systemd autodetect microcode kms modconf block keyboard sd-vconsole plymouth sd-encrypt filesystems)
hm. i don’t have experience with encrypted setups, but it seems like a change of kernel options might also be required in that case:
Oh thanks for your help. Yes, limine.conf has to be altered too.
I dont actually think those particular changes are (yet?) some sort of requirement.
And besides which the mkinitcpio.conf.pacnew file would have been generated something like weeks ago.
But you should definitely, always, and manually, handle your pacnews.
To print them;
pacdiff -o
To manage them;
pacdiff -s
If you want to use something other than the default vim diff;
DIFFPROG=meld pacdiff -s
( Use the v [view] option to open the diff program and apply changes. )
~
❯ grep "^HOOK" /etc/mkinitcpio.conf.pacnew
HOOKS=(base systemd autodetect microcode modconf kms keyboard keymap sd-vconsole block filesystems fsck)
Do I still need to intervene manually?
You likely had or have a pacnew that you could choose to integrate according to your needs.
This appears to be identical to the default.
It is dependent upon your local system configuration whether that is sufficient or optimal.
For more in depth information on this specific pacnew (as it occurred some weeks ago) you may see this thread;
In another example this is used on one machine that does not use encryption or bootsplash;
HOOKS=(autodetect systemd microcode modconf kms block keyboard filesystems fsck)