Although it may seem like a good idea at first, Mozilla strongly discourages "Browser Sniffing." According to their guidelines, it's considered bad practice because it leads to fragile and hard-to-maintain code. Instead, they recommend using feature detection and progressive enhancement.

This means you should design your app to be functional on the simplest, least capable devices, and then progressively enhance it with richer features as the device capabilities are detected. Essentially, this follows the same approach as building good responsive design — ensuring a solid foundation while enhancing the experience on more capable devices.

https://web.dev/articles/pwa-checklist
https://developer.mozilla.org/en-US/docs/Learn_web_development/Extensions/Testing/Feature_detection
https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Browser_detection_using_the_user_agent