On openSUSE Leap 15.3: The system successfully boots up with compress=zstd and zstd compression works. I ran `grub2-install /dev/sda` before I rebooted. Thank you. # compsize /boot Processed 356 files, 486 regular extents (486 refs), 136 inline. Type Perc Disk Usage Uncompressed Referenced TOTAL 87% 76M 87M 87M none 100% 65M 65M 65M lzo 62% 1.1M 1.8M 1.8M zstd 46% 9.3M 19M 19M