I have been testing several apps for my off road drives, and the best solution to date is GAIA GPS:https://www.gaiagps.com

premium annual fees $39.99 will allow use of offline maps, including IGN 1:25000 maps you can use on several devices.

Hardware in use:

• iPad (10.5 pro)
• iPhone smartphones (7, XS, XR, 13…)
• Android tablets (SamsungS)
• Android smartphones (azus, wiko)

-> 32Gb storage for offline Maps and routes is recommanded.

with a Garmin Glo 2 GLONAS GPS bluetooth receiver.

 

Car mount:

Using a mix of great RAM mounts US accessories (phone one inch ball brackets) and other « made in china » gears found on amazon wish or ebay (holders, ball size and gender converters):

Stock windshield handle was replaced by a Ram Mount suction kit, with 4 bolts.