Some plugin is corrupting my upi payment link. How to know which one?

I want to place a upi payment link in this page. However the link starting with upi://pay/?pa=... is converted to https://pay/?pa=...
As a result intended function of the link is not obtainable.

In another installation of WordPress in the same server however such links are processed properly making me suspect some plugin or settings in this site is responsible for changing of the protocol. How can I know which plugin of settings is causing the protocol change?

• This topic was modified 2 years, 11 months ago by Jan Dembowski. Reason: Moved to Fixing WordPress, this is not an Developing with WordPress topic

The page I need help with: [log in to see the link]