Vinyl flooring was installed under front half of depth, but not back half. Older house has some leveling issues so we repaired the best we could. Small dip under stove prevents vinyl from adhering. Original subfloor has poured leveler, is sealed and primed, a layer of lauan, then LVT. So we’re talking about 12”x30” area under back half of range being over top bare lauan. New LG gas range. Fire hazard?
No modern kitchen range is going to have material requirements for the floor. You can put it on a stack of newspaper if you like. Such ovens are used daily in millions of rustic cabins with tinder-dry pine floors, for example, and most ovens have highly flammable dust bunnies the size of, well... bunnies under them. If there were heat and sparks down there we'd all be doomed.
When in doubt, read the manual that came with your new range.