Pacman will never install AUR packages. You need an AUR helper for that.
Pamac does that.
Ok, that is a way to do it, but makes sense only if you want to change things in the PKGBUILD and then always you will take care of it, but since is using DKMS, the module for the kernel was also build?
You never mentioned that before. Is not recognized or is not listing any device? Those are not the same thing.
If is not recognized as command then you have to install xf86-input-wacom package. Is the only one that provides it. Also have to reboot after installing it.
If you respected the steps, then this is what you should see in terminal output (depending what kernel you are using):
pamac build digimend-kernel-drivers-dkms-git
Preparing...
Checking digimend-kernel-drivers-dkms-git dependencies...
Resolving dependencies...
Checking inter-conflicts...
To install (1):
dkms 2.8.6-2 (Required By: digimend-kernel-drivers-dkms-git) extra 54,7 kB
To build (1):
digimend-kernel-drivers-dkms-git 10.r0.gec5c16d-2 AUR
Total download size: 54,7 kB
Total installed size: 177,9 kB
Edit build files : [e]
Apply transaction ? [e/y/N] y
Download of dkms (2.8.6-2) started
Download of dkms (2.8.6-2) finished
Checking keyring... [1/1]
Checking integrity... [1/1]
Loading packages files... [1/1]
Checking file conflicts... [1/1]
Checking available disk space... [1/1]
Installing dkms (2.8.6-2)... [1/1]
Cloning digimend-kernel-drivers-dkms-git build files...
Generating digimend-kernel-drivers-dkms-git information...
Building digimend-kernel-drivers-dkms-git...
==> Making package: digimend-kernel-drivers-dkms-git 10.r0.gec5c16d-2 (Sb 25 sep 2021 12:13:33 +0300)
==> Checking runtime dependencies...
==> Checking buildtime dependencies...
==> Retrieving sources...
-> Cloning digimend-kernel-drivers git repo...
Cloning into bare repository '/var/tmp/pamac-build-b/digimend-kernel-drivers-dkms-git/digimend-kernel-drivers'...
remote: Enumerating objects: 2027, done.
remote: Counting objects: 100% (128/128), done.
remote: Compressing objects: 100% (94/94), done.
remote: Total 2027 (delta 77), reused 55 (delta 34), pack-reused 1899
Receiving objects: 100% (2027/2027), 607.21 KiB | 4.63 MiB/s, done.
Resolving deltas: 100% (1360/1360), done.
==> Validating source files with md5sums...
digimend-kernel-drivers ... Skipped
==> Removing existing $srcdir/ directory...
==> Extracting sources...
-> Creating working copy of digimend-kernel-drivers git repo...
Cloning into 'digimend-kernel-drivers'...
done.
==> Starting pkgver()...
==> Updated version: digimend-kernel-drivers-dkms-git 10.r3.g4762230-1
==> Entering fakeroot environment...
==> Starting package()...
==> Tidying install...
-> Removing libtool files...
-> Purging unwanted files...
-> Removing static library files...
-> Stripping unneeded symbols from binaries and libraries...
-> Compressing man and info pages...
==> Checking for packaging issues...
==> Creating package "digimend-kernel-drivers-dkms-git"...
-> Generating .PKGINFO file...
-> Generating .BUILDINFO file...
-> Generating .MTREE file...
-> Compressing package...
==> Leaving fakeroot environment.
==> Finished making: digimend-kernel-drivers-dkms-git 10.r3.g4762230-1 (Sb 25 sep 2021 12:13:37 +0300)
==> Cleaning up...
Checking keyring... [1/1]
Checking integrity... [1/1]
Loading packages files... [1/1]
Checking file conflicts... [1/1]
Checking available disk space... [1/1]
Installing digimend-kernel-drivers-dkms-git (10.r3.g4762230-1)... [1/1]
Running post-transaction hooks...
Reloading device manager configuration... [1/3]
Arming ConditionNeedsUpdate... [2/3]
Install DKMS modules [3/3]
==> dkms install --no-depmod -m digimend-kernel-drivers -v 10.r3.g4762230 -k 5.13.19-2-MANJARO
==> depmod 5.13.19-2-MANJARO
Transaction successfully finished.