Connection L2TP via IPSec to VPN as PPTP VPN no longer supported on macOS Sierra

How to resolve problem with connection to VPN via L2TP/PPTP on macOS?

Apple announced ending support for PPTP in latest macOS Sierra.

https://support.apple.com/en-us/HT206844: Prepare for removal of PPTP VPN

So the only chance I have is to try it with L2TP via IPSec as my server admin does not offer any other options.

Admin says there is a problem with L2TP/IPSec using on login from macOS Sierra because Apple has got its own implementation for IPSec with its new OS version and common solutions do not work.

Some pages advise to use OpenVPN, but anyway, is there any possibility to connect to VPN with no-longer supported PPTP? Or are they any options to connect with PPTP/L2TP, other than using mac's Network Interface within Network Preferences?

Not open source and not cheap, but Shimo is a way to get back PPTP connections. Is 54 USD though. Be aware though:

Does not support PPTP/L2TP on macOS Catalina

The FlowVPN client is free (and works with any provider).

It supports PPTP and OpenVPN on macOS Sierra:

https://www.flowvpn.com/download-mac/

Just overwrite the FlowVPN server address with any server and it connects.