Lightroom Classic hangs on "Reading Preferences" every launch, works fine in a brand new macOS user account

System info:

• Lightroom Classic 15.4.1
• macOS Tahoe 26.5.2 (also tested on 26.5.1)
• Apple M1 Max, internal SSD
• Catalog was recently migrated during a Lightroom update (Catalog-v13 to Catalog-v13-3)

The problem:
After a recent Lightroom update triggered a catalog migration, the app now hangs indefinitely on the "Reading Preferences" splash screen every time I launch it. This happens 100% of the time in my main user account, on every attempt.

What I've already ruled out:

• Deleted a leftover .lock file next to the catalog
• Fully reset Lightroom preferences (Shift+Option launch)
• Manually deleted com.adobe.LightroomClassicCC7.plist
• Removed all third party plugins from the Modules folder
• Fully wiped the entire ~/Library/Application Support/Adobe/ folder (not just the Lightroom subfolder)
• Deleted all Adobe related entries from Keychain Access (Adobe Lightroom, Adobe.APS, Adobe Lightroom CC, Creative Cloud entries)
• Disabled and quit a third party malware scanner (CleanMyMac) that had background real time monitoring enabled, in case it was interfering with file access on launch
• Tried both signed out/back into Adobe ID and fully offline launches
• Reviewed a Console sample of the hung process, all threads are idle (waiting on condition locks), nothing is actually crashing or looping
• Reviewed the full system log around launch, no fatal errors, just one benign DetachedSignatures warning common across many macOS apps

The key finding: I created a brand new macOS user account (a genuinely clean profile with zero prior Adobe history) and Lightroom launched immediately, no hang at all. This confirms the issue is isolated to something in my main account, but I've already wiped every Adobe related file and credential I can find, and it still hangs there. Whatever's different between the two accounts isn't inside Adobe's own folders or Keychain entries.

Also tried downgrading to Lightroom Classic 15.2.1, which does not hang, but it cannot open my post migration catalog (version too new), so I'm currently stuck choosing between a working older app version with an outdated catalog, or the current version that won't launch at all with my actual data.

Has anyone found what's actually different at the account level here? Permissions, TCC database, something else? Genuinely at a loss for what to try next short of migrating to a fresh user account permanently, which isn't a practical option given how much is tied to my current profile.