Bluetooth 5.0 is pretty new, Dragonboard 410C supports Bluetooth 4.1. 5.0 is compatible with 4.1 but you will not be able to use extended 5.0 features, which does not seem to be a problem for your use-case.
In my opinion, the best way is to use the existing GATT client/server profile. Your device could expose a custom GATT service in which you have one or more characteristics (e.g temperature, pressure…).
Then the dragonboard (as GATT client) would retrieve the sensor data and send them to the consumer.
This is the ~‘official’ Linux Bluetooth protocol stack, BLE/GATT is well supported now. The documentation is a bit limited for beginners, but there are several examples inside the bluez source tree (e.g. gatt client https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/test/example-gatt-client).
In a first time, I suggest you to start implementing the device side (GATT client) and exposes your sensor info. You should be able to test your device against existing GATT client tools like gatttool (linux) or nRF Connect (Android/IOS).
BTW what is the OS on device side ? If you plan to use Zephyr, several peripheral gatt server examples are available in the source tree (e.g. https://github.com/zephyrproject-rtos/zephyr/blob/master/samples/bluetooth/peripheral_hr/src/main.c).