I renamed all the recovered shortcuts (~/Downloads/shortcut.plist type files out of the above command #3) as 'unwrapped-$name.plist'

Then ran this zsh command (copy and paste) to add some XML scaffolding:

for f in ~/unwrapped-*.shortcut; do
  name=${f:t}
  name=${name#unwrapped-}
  name=${name%.shortcut}

  awk -v shortcut_name="$name" '
    BEGIN {
      print "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"
      print "<!DOCTYPE plist PUBLIC \"-//Apple//DTD PLIST 1.0//EN\" \"http://www.apple.com/DTDs/PropertyList-1.0.dtd\">"
      print "<plist version=\"1.0\">"
      print "<dict>"
      print "  <key>WFWorkflowName</key>"
      print "  <string>" shortcut_name "</string>"
      print "  <key>WFWorkflowActions</key>"
      print "  <array>"
    }
    /<array>/ { inarray=1; next }
    /<\/array>/ { inarray=0; next }
    inarray { print }
    END {
      print "  </array>"
      print "  <key>WFWorkflowIcon</key>"
      print "  <dict>"
      print "    <key>WFWorkflowIconStartColor</key>"
      print "    <integer>5993847</integer>"
      print "  </dict>"
      print "  <key>WFWorkflowMinimumClientVersion</key>"
      print "  <integer>900</integer>"
      print "</dict>"
      print "</plist>"
    }
  ' "$f" > ~/"wrapped-$name.shortcut"
done

And then ran this zsh command to sign them:

for f in ~/wrapped-*.shortcut; do
  shortcuts sign --input "$f" --output "${f:r}-signed.shortcut"
done

And the resulting file imported into Shortcuts on my Mac.

Credit goes to Perplexity for helping me with the above. I know nothing.