iPhone XR safari white screen

Safari starting today refuses to come up on a family member's iPhone XR. When we try to launch Safari we get a white screen and after about 8 seconds, screen goes dark briefly, then we see the home screen. When I scroll though open apps, Safari shows up with the white screen. I slide it upward to close it. Very vanilla config, no extensions or vpn. Verified internet connectivity using newly installed chrome. The problem is universal - i.e., not an issue with a particular url. We have tried the following things from various incident reports:

• closed and reopened the app
• rebooted phone after trying each of the below
• turned off WiFi, tried using cellular data
• cleared history and website data (specifying "all history")
• turned off Safari suggestions
• made sure javascript was on; also tried turning it off
• checked phone storage: 52 of 64GB used
• purchased 50GB icloud storage to back up phone prior to trying IOS upgrade
• upgraded to latest IOS 17.3 (was on 16.3) thinking this would also upgrade Safari
• verified there no Safari extensions are configured

Full disclosure Safari has 493 open tabs. Is there a reasonable chance that could be the issue? The owner will only consider closing the tabs after all other reasonable options are exhausted. Have we overlooked anything? I read somewhere tabs would automatically be deleted when reaching 500, which implies it might not be an issue, but I wonder if that is true or if we're possibly bumping into a memory constraint. All other apps such as email and messaging work fine.

Thanks in advance for any suggestions.