Strange. Downloading varnish-6.2.1.tgz with Safari 12.1.2 resulted in a 3,203,620 byte file that failed the shasum check on the three Macs I tried. The file does not appear to be a valid tar.gz file. Downloading with curl and Chrome on the two Macs resulted in 3,207,791 byte files that passed the shasum check. Changing the User Agent in Safari did not fix the problem. Open "safe" files is disabled.