You can try your luck on Austrian's check-in webpage. Quite often it allows to check in for LH flights (and with OS platform, you can do check in 24 hours before departure of the first segment, regardless of whether or not you have a connecting flight).
If that does not work, you should normally wait 23 hours before the connecting flight in order to check in. However, LH check-in software is known for its swingy mood of either allowing to check in even 24 hours before or not allowing to check in ever stating that your flight is being prepared and all that...