Ariel Millennium Thornton @arielmt@computerfairi.es

I still think MDN should add a column for SeaMonkey in its browser compatibility list tables, but I now know the workaround:

Since 2.53.1, the SeaMonkey release notes say it uses the same back-end as Mozilla Firefox 60.x.

So if the browser compatibility number in Firefox's column is 61 or greater, then there's no support in SeaMonkey.