I noticed two things in the crash report: Looking at the crash report that I was prompted to send to Apple yielded the answer.

I could not reproduce the crash when launching Safari with my network connection disabled, suggesting that Safari was hanging on some kind of network request. The solution was to delete my entire reading list. The culprit was a large (over 3,600) number of links stored in Safari’s “Reading List” causing Safari to hit an open thread limit. (Unfortunately, most of the Safari troubleshooting pages that I’ve found were written for old versions of Safari, so the files they suggest trashing aren’t always where they claim.) I tried removing various files under ~/Library that looked Safari-related, but no luck. Safari worked normally there, suggesting that there was a problem specifically with my Safari data in my Mac user profile, or possibly with my iCloud data.

One troubleshooting step yielded a clue: I created a new user profile for my Mac in System Preferences, logged into that user, declined to sign into iCloud, and then launched Safari.

Delete all stored site data (Safari preferences > Privacy > Manage Website Data > Remove All).

Suggestions from Apple’s “If Safari on Mac doesn't open a webpage or isn’t working as expected” article:.

Launch Safari in “safe mode” to disable extensions by holding shift, then clicking Safari’s icon in the Mac Dock.

I’ve tried all the following with no success in fixing it: Even if I open to an empty start page and just let it sit there, it quickly freezes. Within a few seconds to a couple minutes of launching, Safari (version 15.2 on macOS Catalina 10.15.7) freezes with a “wait” cursor (beach ball).

Safari 6.0.5 download for mac