you are not, but you are the first to report this issue. If you search the forum you will find several windows users that had trouble importing the certificates that were solved by following the instructions given by other members of this forum.
I would just like to remind you that there are two editions/versions of the openvpn client available on openvpn.net .
the “official” version - OpenVPN Connect
the Community Edition version
These editions, differ in the way they are configured.
Differences in configuration, have been a source of trouble, reported and explained on the IPFire forum.
My understanding of the client “community” fork is that OpenVPN monetizes their development, which is open source, by selling their cloud or enterprise solutions. The client is designed to work best with those versions that contain proprietary code, including the 2FA.
The community edition is the attempt of porting some of those proprietary features to the open source version.
If you use their cloud or self-hosting solutions, you definitely want to have the V3 of the official OpenVPN Connect. However if you use the open source code, like the server in IPFire, you might want to stick to the community edition.
Quite unlucky too . You hit another problem due to a change to openssl 3 for OpenVPN Connect 2.6 in windows that has not happened yet in IPFire. Fortunately, this post@bonnietwin should provide a work around until openssl 3 is shipped in IPFire.
In my test environment with windows 11 - looks like it’s connected
On windows 10 it did not connect
2023-02-03 20:29:17 CreateFile failed on ovpn-dco device: \\?\ROOT#NET#0008#{cac88484-7515-4c03-82e6-71a87abac361}\ovpn-dco
2023-02-03 20:29:17 MANAGEMENT: Client disconnected
2023-02-03 20:29:17 All ovpn-dco adapters on this system are currently in use or disabled.
2023-02-03 20:29:17 Exiting due to fatal error
Windows 10 connects when all OpenVPNData Channel Offload interfaces are disabled or removed.
OpenVPN 2.6.0 [git:v2.6.0/b999466418dddb89] Windows-MSVC [SSL (OpenSSL)] [LZO] [LZ4] [PKCS11] [AEAD] [DCO] built on Jan 25 2023
library versions: OpenSSL 3.0.7 1 Nov 2022, LZO 2.10
Windows version 10.0 (Windows 10 or greater), amd64 executable
This indeed is an unexpected behavior and DCO should obviously work in Windows 10. I would like to investigate in further. Could you please open an issue for that?