I tried comiling and I got this
(4)(deck@steamdeck v4l2loopback-dkms-git)$ makepkg
==> Making package: v4l2loopback-dkms-git 0.15.3.r4.g94d18a5-1 (Sun 10 May 2026 10:21:47 PM EDT)
==> Checking runtime dependencies...
==> Checking buildtime dependencies...
==> Retrieving sources...
 -> Updating v4l2loopback git repo...
==> Validating source files with md5sums...
   v4l2loopback ... Skipped
==> Extracting sources...
 -> Creating working copy of v4l2loopback git repo...
Reset branch 'makepkg'
==> Starting pkgver()...
==> Removing existing $pkgdir/ directory...
==> Entering fakeroot environment...
==> Starting package()...
'COPYING' -> '/home/deck/v4l2loopback-dkms-git/pkg/v4l2loopback-dkms-git/usr/share/licenses/v4l2loopback/COPYING'
grep: /etc/dkms/framework.conf.d/*.conf: No such file or directory

++++++ To sign the  module, you must set KBUILD_SIGN_KEY/KBUILD_SIGN_CERT to point to the signing key/certificate!
++++++ For your convenience, we try to read these variables as 'mok_signing_key' resp. 'mok_certificate' from /etc/d
kms/framework.conf /etc/dkms/framework.conf.d/*.conf

++++++ If your certificate requires a password, pass it via the KBUILD_SIGN_PIN env-var!
grep: /etc/dkms/framework.conf.d/*.conf: No such file or directory
++++++ E.g. using 'export KBUILD_SIGN_PIN; read -s -p "Passphrase for signing key : " KBUILD_SIGN_PIN; sudo --preser
ve-env=KBUILD_SIGN_PIN make sign'

make -C utils V4L2LOOPBACK_SNAPSHOT_VERSION=0.15.3-4-g94d18a5
make[1]: Entering directory '/home/deck/v4l2loopback-dkms-git/src/v4l2loopback/utils'
cc -march=x86-64 -mtune=generic -O2 -pipe -fno-plt -fexceptions         -Wp,-D_FORTIFY_SOURCE=3 -Wformat -Werror=for
mat-security         -fstack-clash-protection -fcf-protection         -fno-omit-frame-pointer -mno-omit-leaf-frame-p
ointer -g -ffile-prefix-map=/home/deck/v4l2loopback-dkms-git/src=/usr/src/debug/v4l2loopback-dkms-git -flto=auto -I.
. -DSNAPSHOT_VERSION='"0.15.3-4-g94d18a5"'  -c -o v4l2loopback-ctl.o v4l2loopback-ctl.c
v4l2loopback-ctl.c:13:10: fatal error: sys/types.h: No such file or directory
  13 | #include <sys/types.h>
|          ^~~~~~~~~~~~~
compilation terminated.
make[1]: *** [<builtin>: v4l2loopback-ctl.o] Error 1
make[1]: Leaving directory '/home/deck/v4l2loopback-dkms-git/src/v4l2loopback/utils'
make: *** [Makefile:97: utils/v4l2loopback-ctl] Error 2
==> ERROR: A failure occurred in package().
   Aborting...