Looks like ProtonVPN won't have this feature anytime soon. I'd like to share that I use the PCWRT router to split tunnel between two separate VPNs. The router support three VPN protocols, and three concurrent VPN client connections - one for each protocol. To split tunnel between two VPNs, you need to set up two VPN connections. For example, one with WireGuard, and another with OpenVPN. Then you can set up split-tunneling with some domains going through the WiarGuard connection, while other domains going through the OpenVPN connection.
Another neat feature for the router is that you can split tunnel with country code, in addition to IP addresses and domains.
Looks like ProtonVPN won't have this feature anytime soon. I'd like to share that I use the PCWRT router to split tunnel between two separate VPNs. The router support three VPN protocols, and three concurrent VPN client connections - one for each protocol. To split tunnel between two VPNs, you need to set up two VPN connections. For example, one with WireGuard, and another with OpenVPN. Then you can set up split-tunneling with some domains going through the WiarGuard connection, while other domains going through the OpenVPN connection.
Another neat feature for the router is that you can split tunnel with country code, in addition to IP addresses and domains.