@djgalloway: If you haven't removed your previously working older kernel, you should be able to boot into it from the GRUB menu. Another suggestion would be to boot into rescue mode from an Ubuntu 18.04.3 ISO.
@djgalloway: If you haven't removed your previously working older kernel, you should be able to boot into it from the GRUB menu. Another suggestion would be to boot into rescue mode from an Ubuntu 18.04.3 ISO.