If you are using GitHub releases for one reason or another, whether it's because of Android Auto support or something else, follow this guide to receive automatic updates.
Install the Obtainium app found here
Open the app
Tap on the Add App tab
In the 2nd field labelled, "Search", enter bluebubbles-app and click the "Search" button
Select the first result labelled, BlueBubblesApp/bluebubbles-app and then confirm using the "Pick" button
Set any custom configuration/filtering options you may want
Lastly, confirm/save the configuration using the "Add" button at the top
Before installing updates, make sure to confirm the version you are updating to, making sure it is newer.