Comment by no-name-here

> I want to filter all to:`X.X@domain.tld`

You can filter based on the to: field, yes.

For many years I’ve been creating filters on free Gmail for to:, from:, subject:, etc. I set them up on desktop web.

Perhaps there is something more specific you’re trying to do?

> a major feature gap that Gmail (paid or free) cannot create filters on headers.

You can create filters on header fields like from:, to:, and subject:, so I am guessing you mean something different than “cannot create filters on headers”?