I cannot set Let’s Encrypt because of theIPv6 gateway as I was informed by my hosting provider.
However, there is no toggle anymore and I don’t know how to make an API call.
Please help
You need to have cURL or any other tool which allows you to send custom HTTP requests and then simply follow the example posted at Cloudflare API v4 Documentation
Though I’d be surprised if LE did not support IPv6, furthermore they seem to have announced support for it three years ago → Full Support for IPv6 - Let's Encrypt