I am unable to reproduce the build failure locally with sbuild+unshare targetting unstable. Additionally, the build succeeds in Salsa CI and in Launchpad (with an Ubuntu PPA).
I have hesitated to do an upload to Unstable because I didn't want the build to show as failed on all architectures. Marco, do you have any ideas on how to fix this or how you want to workaround the issue? Thank you, Jeremy Bícha

