Unfortunately, the "unknown" browser does not support installing PWAs. To install the application, you need to visit the site from another browser, for example: Chrome, Edge, Opera, Yandex browser, Safari.
No Service Worker support
Possible reasons:
Outdated browser. Follow the link to update your browser and then try installing the application again.
"Service Workers" support disabled. Follow the link and follow the instructions to enable support, then try installing the app again.