I had a couple of .dev domains on Google Domains. Unfortunately, you can't migrate those to another registrar as the .dev TLD is locked to Squarespace. I wonder if they will ever unlock the .dev TLD.
I was just able to finish transferring out my .dev domain from Google to Cloudflare. I had started the process when SquareSpace first took them over but forgot to finish until I saw this, but I was able to transfer out my .dev domain!