Safari on Macbook not working

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Etrecheck – System Information

I'm having an identical problem. I've tried rebooting, turning Safari off in iCloud, and manually deleting the Safari plist, but the problem persists. On my machine it's opening a modal dropdown window asking if I want to import bookmarks from Firefox, but then the dropdown immediate retracts. The app acts like the modal is still present, though, and prevents any interaction. If I could find a way to bring focus back to the modal to make it go away...

I was able to fix this by holding shift while starting Safari; this kept the modal around long enough for me to interact and dismiss it, and it hasn't come back in a regular launch since. The only extension I have enabled in Safari is 1Password (the local version, not 1Password X) - maybe some sort of bad interaction there with the "import from other browser" flow?

Holding shift down worked for me. I had been fighting this for days and tried everything short of a clean wipe of my computer (I did do a fresh install of Mojave).

I have no idea what caused it, but I can rest my weary head now.