

Call your credit card company. Depending on the company/bank, they will either give you a few virtual numbers and/or have the option of having one virtual number locked to a certain merchant or utility company.
There’s MySudo (which I subscribe to) but they charge 3%. It’s basically the same as using Privacy.com. Good luck!
EDIT MySudo is not open-source, sorry.
You’ll have to go through Murena for the Fairphone 4. More details on my comment here about US coverage.