We often go on lengthy roadtrips around Europe and I would like to use those opportunities to contribute to TTN Mapper.
I know of the reference hardware of OpenIOT, but I was wondering, whether there is a more compact solution, than using an Arduino Uno and a GPS shield.
Power supply is not a problem, since it will be used in a car. But it is an old car and does not have USB sockets and I don’t know how stable the current is, when you use a cigarette-USB adapter. Some boards might be very sensitive in this regard.
we currently use TTGO T-Beams for your use case. (It substitutes our initial Arduino+LoRa/GPS-shield tracker and is even cheaper).
I highly recommend to use external antennas for GPS and LoRaWAN/868MHz. I have never had problems with the magnetic mount antennas. An u.fl connector is available at T-Beam for GPS and SMA for 868 MHz.
We have several cars running this way (most still use Arduino Uno + LoRa GPS shield), newer ones already run TTGO T-Beam. (See an example here: https://stefan.schultheis.at/2017/aprs-dragino-lora-gps-shield-70-cm-433-mhz/)
I have no special recommendation. Aliexpress and Banggood work fine but have shipping lead times, there seem to be some IoT specialized shops in Germany who ship it at good prices and you get it within 2-3 days. Also Amazon.de offers it.
Watch out that you order the 868MHz variant for use in Europe.