Conveniently after taking over all of Google Domains too! I missed transferring a couple of domains before the cutover and now I’m in squarespace hell trying to get them out. They make it so much harder by putting artificial delays on everything.
Also, and perhaps Google will finally find this, if you are an OWNER on a SQUARESPACE DOMAIN after the GOOGLE DOMAIN TRANSFER, you can't seem to create MX or TXT or other records.
But if you ADD A NEW USER as a DOMAIN MANAGER then you can create the records, as far as I can tell.
I didn’t need to contact support, but the process requires patience … and some downtime as I had no way of knowing exactly when the transfer happens to recreate the DNS records.
You can setup alternative nameservers first, they clone current DNS settings, then you update nameservers. Do the transfer after.
This worked while they were at Google Domains and about to be transfered. Haven't tried with squarespace yet, but it ought to work