The Mi A1 will never get an Android 10 update but that isn't the end of the road
The Xiaomi Mi A1 has the honor of being Xiaomi's first Android One phone. It was released in 2017 and has already received two major OS updates—Oreo and Pie—as promised by the Android One program. That, of course, means that the Mi A1 will never get Android 10. Or, at least, an official Android 10 build from Xiaomi.
Thankfully, the Mi A1 has a healthy custom ROM scene, and the phone can be upgraded to Android 10 through third-party means. Popular custom ROM Pixel Experience is now offering a stable Android 10 build for the Mi A1.
Pixel Experience is particularly interesting as it seems to be the custom ROM of choice for Xiaomi users looking to ditch MIUI for something more "pure". As the name implies, it's a ROM that gets its origins from Google's Pixel software, which is really as good as it gets.
Those who don't fancy Pixel Experience also have other options in the form of the world-famous (unofficial) LineageOS 17.1, DerpFest ROM., and Corvus OS 5.0. Pixel Experience does seem to be the best choice, though, but takers would be best served browsing the XDA forums themselves.