$ sudo pacman -S linux-cachyos-bore linux-cachyos-bore-nvidia-open
...
$ sudo pacman -Runs linux-cachyos
checking dependencies...
warning: removing linux-cachyos from target list
 there is nothing to do

reboot

$ pacman -Qs linux-cachyos
local/linux-cachyos 7.0.10-1
    The Linux EEVDF + LTO + AutoFDO + Propeller Cachy Sauce Kernel by CachyOS with other patches and improvements. kernel and modules
local/linux-cachyos-bore 7.0.10-1
    The Linux BORE + Cachy Sauce scheduler Kernel by CachyOS with other patches and improvements kernel and modules
local/linux-cachyos-bore-nvidia-open 7.0.10-1
    nvidia open modules of 595.71.05 driver for the linux-cachyos-bore kernel
local/linux-cachyos-headers 7.0.10-1
    Headers and scripts for building modules for the Linux EEVDF + LTO + AutoFDO + Propeller Cachy Sauce Kernel by CachyOS with other patches and improvements. kernel

You have linux-cachyos-headers as well. That depends on linux-cachyos. So that’s why removing only the latter will fail.

Try removing both!

Thanks, solved by

# pacman -Runs linux-cachyos linux-cachyos-headers
# pacman -S linux-cachyos-bore-headers

But some questions:

1. Why doesn’t pacman -Runs linux-cachyos remove linux-cachyos-headers as a dependency which is not depent on by others?
2. When installing linux-cachyos-bore, linux-cachyos-bore-headers isn’t installed as a dependency automatically, it means linux-cachyos-bore doesn’t depends on linux-cachyos-bore-headers, but when uninstalling linux-cachyos it shows that linux-cachyos depends on linux-cachyos-headers, it’s not consistent.