The changing the default search engine is a bit more difficult on the mobile than on the desktop (for example in Google Chrome Android you can not add a custom search engine, you can only select from a predefined list).
Also browser extensions are (mostly) not allowed on mobile :-(
So, the easiest solution to reach mobile users was to add PWA (Progressive Web Apps) features on my existing website https://meta.softwarejourney.net
Once implemented, a mobile user can "install" my website like an application and add an icon to the home screen. 👍