But I think I trust Signal to know the better approach (whichever they ultimately take - they actually said they'd walk "if the alternative meant undermining our privacy commitments".
I don't think it is practical to just refuse to comply with a government like this - especially if you need to charge money (which Tutanota do) and especially if you're nearby, legally speaking (Are Tutanota in Germany?).
And given that Signal has "walked" from other authoritarian regimes but people in those countries still have ways to use Signal, I'm still betting on Signal.