I enjoy mountain biking off-road and often in areas with no cellular. Sometimes I ride in areas with many established trails that cross each other and navigation would help. I looked into bike navigation but they have small screens, are costly, and many of the features are redundant with my Garmin fenix 6x Pro Solar watch. I also never trade in my old smartphones so I have several fairly recent ones laying around. I decided to use my old Motorola Z4 smartphone as a biking navigation using. First I needed a real robust mount. I started on Amazon and found this one.
It grabs all 4 corners and locks in place.
I cleared and reset the phone, removing all unnecessary apps to minimize battery consumption. I also put it in airplane mode, and keep WiFi and Bluetooth off to save power. The Moto Z4 I am using also supports MotoMod batteries, of which I have a few. I am using the 2200mAh unit primarily and I can hot swap in others if it gets low on the trail (which is unlikely). I could also connect the phone to the USB port in the bike display to keep it charged if I wanted. I removed the SIM card as well so it would not search for cellular even out of airplane mode. Then I installed Google Maps, Trailforks, Garmin Explore, and GAIA maps. All of these offer offline maps of bike trails. There are many others too. So far I found GAIA to be the best for bike navigation as it can ever store satellite maps offline.
Here is how I organized the home screen.