Any question answered...

Length+width+height cannot exceed a pitiful 158cm!!!

If they do then it is a 50Euro charge on top. Might as well have gotten the official bike service. But that plane was at 6am and I didn't fancy getting to the airport that early with a bike+luggage. Apparently the cab fare would be about 45euro to the airport!

Wasn't 50euro, was 100euro extra each way!
I gave up looking for rental options or trying to buy a cheap bike over there. Seems Linz is a somewhat desolate and overpriced kinda place.

I contacted lufthansa and they surprised me by saying there was bike spaces where they previously said there was not. So sucked up the 50euro each way, seems like a bargain now compared to the other options. Rental of a decent bike is 30euro per day and they only have them in popular tourist areas/mountains, not in Linz.