I cannot set gestures to work with Smart Launcher (Android 10)
Smart Launcher 6 actually is fully optimized to work with gesture navigation, even if your device says "Not supported by your default home app, Smart Launcher".
The problem is some firmware based on the first versions of Android 10 prevent gesture navigation to work with any custom launchers. In December 2019, Google released a patch for Pixel 2, 3, and 4. Samsung, One Plus, and other manufacturers distributed this patch to their devices with a software update starting from the start of 2020.
If you have problem setting navigation gestures, please check you are using the latest software available for your device. If yes, we suggest continuing using the three-button navigation until a new software update will be available from your device.
Today, some manufacturers like Xiaomi still haven't addressed the issue. You can check the relevant page for details.