As I’m running iOS 26 and Sonos S2 without issue, I suspect this is a red herring. What I do suspect is some sort of network issue. You may want to confirm your router is sending an appropriate network signal that the PLAY:1 can ‘read’, by checking the Sonos Network Requirements FAQ. And, in case there’s been some sort of failure of the WiFi components in the PLAY:1, I’d connect it with that Ethernet cable, then submit a system diagnostic, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here, they get sensitive about GDPR.
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.
When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.