linux-postmarketos-allwinner can't be built - source tarball is 404

As of 2023-09-07, megi has emptied out their kernel repository on GitHub: https://github.com/megous/linux (archive, announcement on their blog). As a result the linux-postmarketos-allwinner package can no longer be built because the https://github.com/megous/linux/archive/$_tag.tar.gz tarball is 404.

Their gitweb host at https://xff.cz/git/linux doesn't have snapshots enabled, so something like https://xff.cz/git/linux/snapshot/orange-pi-6.4-20230731-1920.tar.gz cannot be used.

In https://xff.cz/kernels/git/README they suggests an alternative method using a git bundle, but this requires a (non-shallow) git clone of torvalds/linux . Also the bundle won't have a stable checksum so it can't be used as a source anyway.