Looks like Austrian are in the process of switching the OS2577/2578 INN-MAN-INN from pure charters to scheduled services.
The flight has now started appearing in GDS (to which it previously hasn't) and also gains a 2nd weekly flight on Sunday's. It doesn't appear on Austrians website yet.
OS2577 INN 0805 MAN 0925
OS2578 MAN 1110 INN 1430
Saturday's A321
OS2577 INN 0825 MAN 0945
OS2578 MAN 1045 INN 1405
Sunday's A320
The Sat flight is bookable all winter, the Sun flight starts 7th Jan.
VIE remains 5 weekly E190/A319 but the new flights mean Austrian will have 2 flights Sat and Sun from Feb.