ehh... it's been known for awhile that protonmail is in the pockets of the US government so it's not really a loss for the russian people.
What they should be using is either Streisand[0] email with a server in a country that respects their privacy(neitherlands, panama, etc) or lavabit email[1].
I didn’t know they had “support centers in San Francisco, CA, and Skopje, Macedonia” [1]. Thank you.
Still a far cry from proof of being “in the pockets of the US government” [2]. Signal, too, has American nexuses. That doesn’t automatically render it compromised.
What they should be using is either Streisand[0] email with a server in a country that respects their privacy(neitherlands, panama, etc) or lavabit email[1].
[0]: https://github.com/StreisandEffect/streisand [1]: https://lavabit.com/
EDIT --
Sorry streisand doesn't in fact have an e-mail server. I thought it did at one point. I guess you can use mail-in-a-box(https://github.com/mail-in-a-box/mailinabox).