Hi, I confirm that a manually built packages with 2.3.8 sources and the addition of --askpass in DAEMONARG works fine (without this addition it did not work, as 2.3.8 fixed the use of this option, but it is not used in the package startup script).
I guess --askpass should be also added in openvpn@.service, but I did not test that as I am not using systemd. Cheers, -- Damien Wyart