Are you able to temporarily connect your PlayBase via an Ethernet cable?

Then i would need to “tear down” my nice setup in the living room with hidden cables etc… the router is far away from the living room

any othe option before I do that?

Connecting any Sonos device via an Ethernet cable could work and then changing your wi-fi credentials. Otherwise, the only other option is to change your new router SSID and password back to that of your old router and reset your password in the Sonos App back again.