After trying to find an app with something even close to Spotify Connect I gave up and switched to Apple Music and replaced my speakers with newer Denon that have Apple streaming support.
It was the choice between letting Spotify fuck me over again and again and spending a few hundred dollars on new speakers. Annoying but fuck Spotify and their relentless upsells, ads, podcasts, books, etc
(I feel pretty strongly about that because I used it daily since they released their beta version close to two decades ago).