I guess you did not fly Southwest last winter.
So you booked this yourself flight directly with United, and because UA does not fly from FLR, that leg was with Air Dolomiti? Sounds like a problem with that airline, not UA. Are you sure any of your legs are actually with UA and not LH?
And no, you are not getting a seat upgrade because of this.
And if you want to control your flights, you can book them directly yourself, not use Viking.