I want to suggest email providers focused on security like Protonmail, Tutanota, Mailfence, etc. to put in place a canari email warning system to propose to their clients.
This is how this would work: you subscribe to their service and every Monday or every 1st of the month you receive an email that tells you something to the effect of "We are happy to announce to you that to this day we have not been subpoenaed to provide any information regarding your account."
That way the day they do receive a subpoena with a gag order of course they can't legally warn you that you are under surveillance, but they just don't send you your weekly / monthly email anymore and now, if you are attentive, you know something is going on.
I think that should be legal pretty much anywhere in the world, right? They can prohibit you from warning someone, but they can't attack you for NOT sending a false declaration in your name. Maybe someone more familiar with laws can chime in on this.
"Canari emails" of course because of the proverbial but also very real canaris in coal mines.