There's someone who tested it recently, had a few issue but in the end, it worked.
Some of the issues includes:

• His Bech32 address (bc1) wasn't accepted by coinb.in.
• Problem with the construction of the Raw Transaction.
• Problem with signing.
• Undisclosed timezone issue.

Here's the 1st thread: Is there a service that lets you lock your Bitcoin for 24-48 hours etc.?
The second thread: Coin stuck in Coinb.in and there is no way of getting it out

If you're planing to use it for high-value transaction, I don't recommend you to use this service.