tel, wtail, ext:tel, ext:wtai, etc. The currently commonly used telephone protocols are as follows:

Of course it depends on the mobile phone model, mobile browser, etc. It is not supported but it is beneficial to search engines

Two possible situations:
1. The browser does not support this attribute
2. The browser does not have permission to make calls
It is recommended to check whether the browser supports this attribute before taking downgrade measures. You can use Modernizr's Modernizr.inputtype.tel to detect it.