I have a pretty minimalist set up.
Bubbler GPS on an Android phone linked to Spotwalla. My Bubbler is the upgraded account that saves data when I have no cell service and up loads it when I do have service (I think I have this correct). It was the same set up I used for the 2021 HoT Rally with the caveat that Spotwalla is changing.
Question: is this sufficient for the LDX Rally or should I upgrade to a Spot device/Spotwalla?
As long as your points show up on Spotwalla, that will be fine. Granted, a satellite tracker is not dependent on phone data service but since other rallies are allowing people to move away from Spot devices, we allow it too.