If you’re like me and like to track your cars and look up the cars in your garage outside of the game check out my Car Tracker for Forza Horizon 4. It’s a useful reference for checking for deals at the auction. Feedback is welcome, although now that the game is out it may be a little while before the next update. 
You can get it in Google Play here: https://play.google.com/store/apps/details?id=com.thumbpowered.msohm.cartrackerforforzahorizon4
I also made one for FH3, if interested read https://forums.forza.net/turn10_postst119270_Android-Car-Tracker-for-Forza-Horizon-3.aspx