Hi Jordan,
am building the new OpenVPN-2.5_* versions since Beta 1 but this messages appeared only since Beta 4 which is at that time the actual one. Have integrated a lot of stuff in ovpnmain.cgi meanwhile and my whole environment runs only in 2.5 environment. The whole error message i got is this:
openvpnserver[21442]: DEPRECATED OPTION: --cipher set to 'CHACHA20-POLY1305' but missing in --data-ciphers (AES-256-GCM:AES-128-GCM). Future OpenVPN version will ignore --cipher for cipher negotiations. Add 'CHACHA20-POLY1305' to --data-ciphers or change --cipher 'CHACHA20-POLY1305' to --data-ciphers-fallback 'CHACHA20-POLY1305' to silence this warning.
where also a explanation is included on how to fix it. The --data-ciphers error/development is a problem whereby updated clients does not worked with OpenVPN servers with <= 2.4.x versions. In this situation it might be the best to downgrade your client since the development of the new OpenVPN version is not completed it won´t be come up in an IPFire Core update.
Nevertheless if you want to test it have the compiled OpenVPN-2.5_beta4 here, it also not that hard to build it by yourself and i can deliver you an updated ovpnmain.cgi <-- but remember this is a testing environment even i use it also in production without problems !
Best,
Erik
EDIT: The --auth directive is here active but there are no error/problems nor i have seen something in the announcements for such changes. If you have more on it, please post it here.