The Wild Shape feature includes the following:
[...] if you revert as a result of dropping to 0 hit points, any excess damage carries over to your normal form. [...]
Meanwhile, the absorb elements spell reduces damage taken, even the triggering damage source. And from the spell description we can also see the following:
1 Reaction [...] which you take when you take acid, cold, fire, lightning, or thunder damage [...]
So what happens if a low level Wild Shaped Druid has 10 HP left in their Wild Shape form and takes 30 fire damage?
They cannot cast the spell at first because they are in Wild Shape, but then, after 10 damage, they revert to their normal form. Can they then cast the spell?
If they can cast the spell, does it only impact the remaining 20 damage or does it have some sort of retroactive effect on the damage they already took?
If it does have a retroactive effect, what happens if they initially only took 16 damage?
How does the absorb elements spell interact with Wild Shape?