First attempt on a workaround.

debian/changelog

@@ -1,3 +1,10 @@
+livecd-rootfs (2.765.47) UNRELEASED; urgency=medium
+
+  * Explicitly remove v4l2loopback packages to workaround issue with tasks
+    and seeds. Should fix build failure (LP: #2079803).
+
+ -- Łukasz 'sil2100' Zemczak <lukasz.zemczak@ubuntu.com>  Fri, 06 Sep 2024 10:50:02 +0200
+
 livecd-rootfs (2.765.46) jammy; urgency=medium
 
   * Add 6.8 kernel apparmor features' preseeds. (LP: #2074204)

live-build/auto/config

@@ -823,6 +823,9 @@ case $PROJECT in
 
 	ubuntustudio-dvd)
 		add_task install minimal standard ubuntustudio-desktop ubuntustudio-audio ubuntustudio-graphics ubuntustudio-video ubuntustudio-photography
+		# To work around the fact that v4l2loopback-dkms is still pulled in (via tasks) even though no longer present in the seeds
+		# Fixes build failure
+		remove_package install v4l2loopback-utils v4l2loopback-dkms
 		COMPONENTS='main restricted universe multiverse'
 		case $ARCH in
 			amd64|i386)	KERNEL_FLAVOURS='lowlatency-hwe-22.04' ;;