I committed precisely the same error as the OP here, in that I ordered a Mini 3 the instant DJI announced that an SDK release for the Mini 3 and Mini 3 Pro was imminent. At the time I simply refused to consider the possibility that beyond-RC signal range flights might NOT be possible even if Litchi gained access to the Mini 3 and Mini 3 Pro SDK.
Come to find out the SDK that DJI will release for the Mini 3 and Mini 3 Pro will NOT allow the drone to complete waypoint missions once signal connectivity between the RC controller and the drone is interrupted. I had been seduced by that phenomenal 45-minute flight battery duration for the Mini 3, and therefore, in full wishful thinking mode, I hurriedly placed an order for the Mini 3 due to my own unfounded supposition that Litchi would work beyond signal range with the Mini 3 just as it does with DJI’s older drones listed above by another reader.
If the OP has deep pockets whereby cost is no object I would like to suggest an option worthy of consideration for the “let them eat cake” demographic, which would entail contacting DJI and offering to TRADE IN that Mini 3 Pro for a Mavic 3 costing twice as much, BECAUSE the Mavic 3 is now confirmed to be capable of completing waypoint missions despite RC signal loss, using DJI Flly and not Litchi.
So, OP, I sayeth verily unto thee that if thine hath $1,500 burning a hole in thine pocket, then tarry not and buy a Mavic 3 now, without delay. Alternatively, if the OP is a mere mortal for whom the price tag does matter, he could consider selling the Mini 3 Pro as a nearly new offering, in order to raise the $700 that would cover the cost of the superb Mavic 2 Pro in lightly used condition.