In the snapcraft.yaml definition, you can change some of the make variables:
I’ve changed the MIRROR below, for example:
make-parameters:
- KERNEL_SOURCE=focal:linux-uc20-efi
- KERNEL=linux-pc-image
- KERNEL_IMAGE_FORMAT='$(if $(filter x86_64,$(shell uname -a)),efi,vmlinuz)'
- PROPOSED=true
- MIRROR=gb.archive.ubuntu.com/ubuntu
build-packages:
- debootstrap
- gnupg
- kmod
- lsb-release