This is honestly so confusing. I just closed the channel so which channel do you suggest now that supports keysend payments?
Even if you open a channel to a node which supports keysend payments, you still won't be able to send them to any node. The destination node needs to have them enabled. I believe that LND nodes still don't accept keysend payments by default. Such nodes must give you a payment invoice if they want to receive coins from you.
I tried sending a keysend payment to both of these nodes from my c-lightning node and I got the same error. Once you open a new channel, you can try it with my node. It should work.