In theory, there should be no reason that you should be unable to use an external GPS device that connects to your iPad via Bluetooth or WiFi - and this is often necessary where direct reception of GPS signals are screened from the iPad/iPhone. The external receiver is simply a BT/BTLE accessory.
A typical implementation would be in an GA aircraft cockpit. The key to successful use would be to ensure that the target App can accept input from the external receiver. As for integration at a system level, this should be clearly stated in the GPS receiver specifications.
Here is a link to an external article that you might find informative:
https://ipadpilotnews.com/2019/12/how-to-choose-the-best-gps-ipad/
I hope you find this to be helpful.