Hello. For the record: I can build this package just fine using the unshare backend.
Moreover, if the current title was correct (as in "every time we try the build using the unshare backend, the build fails"), then this bug would be RC, because the buildd network has switched to using the unshare backend at least for trixie and above. So, my feeling is that there is no bug in phosh-mobile-settings at all. Lucas: Can we investigate what are we doing differently so that this package fails for you and not for me? Are you sharing /tmp between simultaneous sbuild invocations? Thanks.