1: Add the VPN connection as normal using the Network Manager GUI

2: Edit the connection file in /etc/NetworkManager/system-connections/(connectionname).nmconnection where (connectionname) is the name of your VPN conection

3: In the [vpn] section, beneath the line that starts ca=, add a new line reading

tls-cipher=DEFAULT:@SECLEVEL=0

4: Save the file

5: Enter the command systemctl restart NetworkManager

6: Start the VPN connection as normal and it should connect (mine did anyway and I verified it by checking my IP and location)

Upgrade Your VPN settings to new one. 🙂

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Dodatek:
This is the solution!
I uncommented these lines in /etc/ssl/openssl.cnf:

[openssl_init]
providers = provider_sect

[provider_sect]
default = default_sect
legacy = legacy_sect

[default_sect]
activate = 1

[legacy_sect]
activate = 1

and the connection worked immediately. Many thanks!