You can use rclone to sync your data with Proton Drive and vice versa. But the chances are high, that you also have Proton VPN, which ironically will not let you use access your Proton Drive through VPN! But there is a simple solution. You can use rclone’s --bind argument with your local IP address to bypass the VPN.
The following synchronizes the remote drive with the local drive in home:
rclone sync ProtonDrive: ~/ProtonDrive/ --verbose --bind 192.168.1.xy