Use APKPure App
Get Assistant Quick Settings Tile old version APK for Android
Starten Sie Ihre Standard-Assist-App über den Benachrichtigungsbereich
This app provides an alternative way to launch the assistant on devices with no home button to long-press.
It has no launcher icon, you have to add it to your Quick Settings tiles. Look for the pencil icon in the notification shade. You also need to set a default assist app in your device settings.
Source code is available at https://github.com/bndeff/qsassist