Ok, so there’s a simple workaround for this one (until it gets fixed)
Install an eSIM app called “Dent”, this gives you a small amount of esim data for free. Create an account, and let it set up the esim (choose “primary” for all options to make sure you’re still using your physical sim for everything).
Once set up, you’ll see the prompt in settings has gone.
Now, use Settings->Mobile Data and tap on the Seconday sim and turn it off.
You’re now left with your physical sim being the only active one and you’re not paying anything for your esim.
Hope this helps.