ProtonVPN would've helped. From article:

"ProtonMail also operates a VPN service called ProtonVPN and points out that Swiss law prohibits the country's courts from compelling a VPN service to log IP addresses. In theory, if Youth for Climate had used ProtonVPN to access ProtonMail, the Swiss court could not have forced the service to expose its "real" IP address. However, the company seems to be leaning more heavily toward recommending Tor for this particular purpose."