Imo Vegas is the only possible destination if it is true the Bobby Ryan's deal is attached.
Bobby Ryan is not a LTIR candidate. He is playing badly but he is playing. He's only 31.
Ryan has a cap hit of 7.25 AAV for 4 more seasons. Ottawa is already retaining on Phaneuf, so I doubt they would retain on Ryan considering you are only allowed to retain on two deals at once, so that would paralyze them on retention for a long time. (edit: I was wrong about two retentions. You can have 3. So maybe this is an option, although it leaves Ottawa paying a lot of cash in retention deals, which defeats their purpose a bit)
Karlsson has 6.5 AAV, but it is about to be 12 AAV in one more year, and that's conservative considering he said he's not interested in a discount of any sort.
Any team trading for Karlsson could send salary the other way, but the whole point of this trade is for Ottawa to shed salary, so it would still be very lopsided in terms of cap leaving Ottawa.
Ryan has a NMC. He would need to be protected in the Seattle expansion. No team would find this acceptable except Vegas, since they don't have to participate in the Seattle expansion.