You uninstall and install with the packetmanager pacman
pacman -S linux66 to install a LTS Kernel
pacman -R linux65 to remove your current kernel
You can get anytime the help page from a command, ie. man pacman where it shows you all the commands for a program.
LTS means LongTimeSupported Kernel, all others between are only for developement and have a shorter time, where they are supported.
Then reboot, if you still got problems, you have to remove plymouth, i dont know, if it is fixed right now.
You could temporally boot the kernel until your GUI despite plymouth is installed, when you press e when grub loads, remove “quit splash” from your kernel line, then boot with F10.
Or you simple switch again to a TTY and remove it from there.
But my guess is also, when you just remove it right now from your 6,5 Kernel, it may will boot then,
if you know, how to edit grub. If it is to difficult, just install Kernel6.6 and remove plymouth.