I've tried several phone apps to use as live view monitors with various m43 format cameras with mixed results to the point where I rarely used them during project shoots. I've had an Action 3 camera for a few weeks and finally tried the DJI Mimo app on an iPhone and find that it works very quickly and reliably. It is totally usable in the field to both check framing and to make adjustments to the camera before hitting the record button on the iPhone. It also has a zebra indication for overexposure that is useful for setting exposure, especially when shooting D-Cinelike 10 bit h.265 and the Leeming Lut Pro exposure guidelines.
The connection is quick and not fiddly at all. After the initial first time connection, anytime the camera is powered on, one can open the app, hit connect, join the network, and the camera view shows up on the phone in just a few seconds. No need to do anything at the camera itself. Exiting the app lets the camera keep running with no interruption or changes. You can reconnect any time without disturbing the recording. Wonderful. I wish it was this easy on an Olympus or Sony camera! Maybe I should try the apps again with my more recent cameras, hopefully some improvement have been made and I am just late in trying them.