It’s pretty hard to kill an apple tree, so it will survive. I would treat it for pest with a dormant line sulphur spray and then immediately use pruning sealer tar to patch the crack to prevent any insects from harboring to cause damage. In a year or so it should be able to refill the crack as new bark grows just as it has grown over prior pruning scars. I have a cherry tree that did a similar trick and it is now healing
Could something have hit that limb that is coming from the trunk at that spot? Seems like a hard blow from the side- like someone running into that limb of the tree, could create a lot of strain and might open the main trunk like that.
I’d probably prune that big limb off because that will put a lot of force on the tree at the spot it attaches. Between that and the cicada damage your tree has been through a lot!
Good, at that size it’s easy. If it were mine…I would shine a light into the cracks to make sure there is no bugs or mold/fungus in there(which there shouldn’t be this time of year). If all clear, I would just tightly wrap the cracked regions with some flagging tape, or green garden tie tape, or you could even use electric tape but flip it over so glue side is up. Wrapping 2-3" beyond each end of the crack.
This will keep the bugs, spores, and water out and keep the wound just right for fastest healing. Just like a big grafting site. No sprays or coatings needed. If halfway through the summer it looks it’s bulging too much beyond the tape you can take it off and re-wrap with less pressure. Should be completely healed and removed next spring.
If it were mine I would leave the split alone (or maybe shave the very edge of the split with a super sharp knife to speed healing) and whitewash the trunk up to 2 or 3 ft just in case it was a winter/sun injury. Use of sealer is no longer advised as it seals in moisture and invites rot, to the best of my knowledge. It almost looks like a lightning strike.
I have seen this on trees that have been either through a drought and then gotten a huge amount of rain all at once or in the spring during the time between a really cold winter and spring getting a lot of water.