Display URL Not Working on chromium-browser, RaspberryPi

Roon Core Machine

Synology 218+
DSM 6.2.4-25556 Update 3

RoonServer running on USB SSD

Networking Gear & Setup Details

Synology connected to home network via ethernet and generic TP switch
Ethernet from switch to Raspberry Pi

Connected Audio Devices

Raspberry Pi 4
Rasbian x64 (bullseye)

Number of Tracks in Library

~60k

Description of Issue

I’m building a new Raspberry Pi streamer with a 3.5" TFT screen running Roon bridge. I’ve made a handful of these with different UIs, and for this one I’m looking to run chromium-browser in kiosk mode connected to the Roon display URL (http://192.168.1.20:9330/display/ in my case).

The display URL will not render in chromium-browswer on a RaspberryPi at all, but chromium-browser on the Pi works fine for any other website I’ve tested. See screen shots below. For the Roon display URL it just sticks perpetually in “Loading…” and never renders the page. This happens in either stand-alone or kiosk mode. The Pi can see that URL just fine, I can curl it from the CLI and I get the page back as expected so there’s no issue with networking, And the display URL works on every other device without issue, it’s just not working in chromium-browser. I can load the same Display URL on a Mac with Chrome or Safari, on the same network, also ethernet, and it renders fine. I believe that the Display URL used to render fine on a Pi chromium-browser, as far as I remember, so has something changed?

$ chromium-browser --enable-features=OverlayScrollbar --disable-restore-session-state --kiosk --noerrdialogs http://nugs.net [WORKS]

$ chromium-browser --enable-features=OverlayScrollbar --disable-restore-session-state --kiosk --noerrdialogs http://192.168.1.20:9330/display/ [DOES NOT WORK]

$ chromium-browser --noerrdialogs http://192.168.1.20:9330/display [DOES NOT WORK]

This issue appears to be limited to the latest Raspbian release, Bullseye, and/or the version of chromium-browser that ships with Bullseye (as of this writing, which I believe is 98.x). Reverting to Buster, which downgrades chromium-browser to 95.x, works as expected and the Display URL renders just fine.