Is it possible to run another VPN connection alongside Mullvad?

My use case:

• Linux distro
• Mullvad is always on
• Additional VPN that just adds networks (openvpn3 with a .ovpn file)

Currently, openvpn3 cannot connect if Mullvad is on. If I turn Mullvad on after the openvpn3 connection is established, the latter stops working.

Is it possible to have both connections, and how?