Blank/gray modal overlay blocks UI in Acrobat 26.001.21691 (Windows) — persists after repair, cache clear, DNS/registry fixe

Hi, I'm seeing the "Black screen after sign-in" — solid gray/black overlay blocking the UI, both on the Home screen welcome dialog and inside the document view after Sign-in — but wanted to flag that it persists even after a completely fresh install, which may be useful for others hitting this.

Environment: Acrobat 26.001.21691, Windows 11 Home 10.0.26200, Intel Arc 140T integrated GPU, no third-party AV/EDR (Windows Defender only), no proxy.

What I've tried, in order, with no effect on any of them:

1. Force-closing all Acrobat/AcroCEF/AdobeCollabSync/WebView2 processes and relaunching
2. Full Repair Installation (as Administrator) — completed with no errors
3. Deleting the WebView2 profile cache (%LOCALAPPDATA%\Adobe\Acrobat\AVWebview2\DC\EBWebView)
4. Confirming network connectivity to acrobat.adobe.com / cc-api-data.adobe.io / www.adobe.com (all reachable)
5. Setting the FeatureLockDown registry keys to suppress in-product messaging (bAcroSuppressUpsell=1, bMerchandizingEnabled=0, bToggleSophiaWebInfra=0, bToggleFTE=0, plus cIPM\bShowMsgAtLaunch=0 and cIPM\bDontShowMsgWhenViewingDoc=1)
6. Adding a secondary DNS server after seeing one DNS timeout to cc-api-data.adobe.io in the event log
7. Full clean removal of Adobe Acrobat and Adobe Creative Cloud (via their own uninstallers), deleting all leftover files under Program Files and AppData, then a completely fresh install from Adobe's site — same issue reappeared immediately on first launch
8. Updating the Intel Arc GPU driver (32.0.101.6458 → 32.0.101.8861)
9. Fully uninstalling and reinstalling the Microsoft Edge WebView2 Runtime (system-level, via the Evergreen Bootstrapper)

Since this reproduces on a totally fresh install with a current WebView2 Runtime and current GPU driver, it doesn't look like local corruption — something in the panel's content delivery or rendering pipeline seems to be failing for certain environments. Would appreciate any pointers, and happy to share Process Monitor logs or a fresh crash dump if that helps track it down.