Star Alliance alternatives
You will have no problem using your UA Gold card for the balance of the year - as many of us former Aeroplan Elite customers can attest!
The Star Alliance carriers most recommended when I switched incl. Aegean & TK. Has this changed? One to avoid is AC/AP - the min spending requirements and the min AC metal rules will mean you won't see the inside of another lounge! Have you considered the Priority Pass lounge card?