Although Tunnelblick usually uses one of the versions of OpenVPN that are embedded in the Tunnelblick.app, Tunnelblick will also allow the use of any OpenVPN versions that are contained in
and have a specific structure and naming convention.
You might be able to use the OpenVPN/OpenSSL version you want from Tunnelblick 3.7.3, which has the correct structure and naming convention.. Look in that version's Tunnelblick.app/Contents/Resources/openvpn folder for a folder with a name like "openvpn-.x.y.z-openssl-10.2l" (not sure what the x.y.z are). Copy that folder into /Library/Application Support/Tunnelblick/Openvpn. (Create it if necessary, and make sure the folder and all its contents are owned by root:wheel.)
The next time any version of Tunnelblick is launched you should see the additional OpenVPN version as a choice in the drop down list of OpenVPN versions..
Two possible catches:
- This may not work if the digital signatures on the OpenVPN binaries are not accepted by more recent versions of macOS.
- This might work without doing anything on M1 Macs, or it might be necessary to set Tunnelblick.app to "Open using Rosetta" (in the Finder's "Get Info" box for Tunnelblick.app).
Good luck, and please report back with your results.