Safari video buffering/black screen on Wi-Fi — any fix?

Hi everyone,

Video playback in Safari broke after updating from macOS 26.7.1 to 27.0.1.

**Symptoms:**
– Safari on Wi-Fi: Web players show a black screen, YouTube buffers constantly.
– Chrome on the same Wi-Fi: Works perfectly.
– Safari on mobile hotspot: Works perfectly.
– Rolling back to 26.7.1: Everything works fine in Safari.

**Already tried (didn't help on Wi-Fi):**
– Custom MTU (1450, 1280, etc.)
– Private Relay & "Limit IP Tracking" disabled
– Custom DNS (Cloudflare, Google) & IPv6 disabled
– UDP blocked via Terminal / packet filter
– Sysctl network tweaks & router QoS disabled

Is there a known fix for this on 27.0.1 without switching to Chrome or rolling back?