See my calamaris package
Arch Linux
The beloved lightweight distro
Instead of manually patching the package maybe create an own/local package for it and maintain it on your own and include your patches.
this task is easy on gentoo but hard anywhere else
in the past I checked package updates via nvchecker, grabed the latest PKGBUILD via ABS, applied the patch, compiled the package and sent it to my custom repository
if you add the repository higher in your pacman.conf it will grab it from that first
but this a huge pita, even going through the route of maintaining an AUR package is simpler
this task is easy on gentoo but hard anywhere else
Not true, it's also doable on NixOS: https://nixos.wiki/wiki/Overlays#Adding_patches
Pacman downloads and installs binary packages. You cannot use it to build packages with custom patches.
I think pacman hooks could help you
Could you explain more? Sounds interesting. I thought hooks were only actions applied post install?
I'm not very familiar with them, I mostly just know they exist. https://wiki.archlinux.org/title/Pacman#Hooks has information on them
I also just found this wiki page https://wiki.archlinux.org/title/Patching_packages btw, might help maybe