Connect to SSL-VPN without installing SoftEther VPN

[a.woll]

Based on my experience you'll always need a virtual network adapter.
I used long time ago a VPN concentrator by Netgear.
It deployed an isntant client downloadable over https and this client installed an virtual tun interface, too.

If you want to use a built-in client in Windows, perhaps SSTP will fit your needs.
It can be handled by the internal windows client, you won't need any installation but a certificate has to be deployed to the clients.

Perhaps one issue:
SSTP needs ports 80 and 443.
Some admins block the initial connection of SSTP on port 80.