Use Legacy SSL VPN Client with XG Firewall

No, that is not possible. The reason is, you cannot migrate the user certificates to XG Firewall. Therefore the certificates are invalid and are dropped. 

What you can do: Uninstall with a script the SSLVPN client and install Sophos Connect. Then roll out one provisioning file to all clients in the same script. User can then use the new client to connect to Sophos firewall. 

made a script for this: https://community.sophos.com/sophos-xg-firewall/f/recommended-reads/128936/sophos-connect-migration-script-from-utm-sslvpn 

Hmm, couldn't belive that, because of all certificates are stored in the .ovpn-File.

So i created a test-environment, and the result is, that users still can connect to XG Firewall, using the SSL-VPN-Client from UTM.

They just need to download a new configuration / .ovpn-File (as i wrote in my first post when asking).
No Sophos Connect or other new Software is needed.

If you download a new ovpn File, you basically have a new certificate. Therefore you basically roll out a new user? 

I assumed you are talking about the old certificate / config files. This is not possible. But the Client (the installer) is the same. 

If you download a new ovpn File, you basically have a new certificate. Therefore you basically roll out a new user? 

I assumed you are talking about the old certificate / config files. This is not possible. But the Client (the installer) is the same. 

Think we have to define "new user" ;)

For my Company it's still the same user, because of we're using Active-Directory sync.
But of course, for the SSL VPN Client it's like a new user after XG-miration, because of he need new certificates.

As long as the User after migration can connect to the XG user portal and download the config-file by himself, migration is much easyer for us, because we don't need to coordinate the roll-out of new software to all clients.
That's why i asked.