I didn't quite have Dan's patience, but FWIW my system successfully rebooted 25/25 times with the systemd package (237-3ubuntu10.42) from bionic-proposed in combination with libseccomp2:amd64 (2.4.3-1ubuntu3.18.04.3) installed and syscall filtering enabled in /lib/systemd/system/systemd-resolved.service.
I didn't quite have Dan's patience, but FWIW my system successfully rebooted 25/25 times with the systemd package (237-3ubuntu10.42) from bionic-proposed in combination with libseccomp2:amd64 (2.4.3- 1ubuntu3. 18.04.3) installed and syscall filtering enabled in /lib/systemd/ system/ systemd- resolved. service.