Just want to chime in that you can check on the Apple website how much you'll get for your G8 on trade-in. Looks like you'll get $60, assuming the phone is in decent condition.
Tell your wife you're planning on buying a $200 dongle/DAP if you have to get rid of your old phone. If she wants you to trade your old LG for financial reasons, you'd save $140 by keeping it.
I just switched from a Samsung Galaxy S9 to the iPhone 12 Mini and am pretty happy with the switch. After a certified repair shop broke my S9's motherboard and refused to fix it without charging me "a lot" (their words), I decided to make the switch.
Personal opinion: just start with the Lightning dongle and see where that takes you. I just plugged in my DT 1990 (250Ω) and it sounds great and gets them louder than I like to listen (though without terribly much room in the volume control). I've used a FiiO BTR5*, an AudioQuest Dragonfly Red**, and an old FiiO X5+E12A*** stack and to me the Lightning dongle sounds just as good as any of those and costs way, way, way less.
If you decide to use the dongle, you just saved $191. If you decide to buy something else, you only wasted $9.
* I do not think the BTR5 is a very good product and wouldn't really recommend it. You can buy twelve Lightning dongles for the price of one BTR5.
** I liked the DFR when I used it, but in retrospect it was a total ripoff and also not a very good product. It broke just after the one year warranty expired. You can buy 22 Lightning dongles for the price of one DFR, and each one will be a better product than the AudioQuest. In my opinion, of course.
*** The original X5 is what has turned me off from modern DAPs. What a hunk of junk. Sounded like trash and the UI was even worse than the sound. The firmware was even worse than that. The E12A made the whole sound much better, but it ended up weighing 8 ounces (226.8 grams)! You could buy 55 iPhone dongles for the price of this stack and it would still weigh less than half! And sound as good!
I realize that the X5 isn't made anymore and that possibly newer DAPs are better in every way, but the experience with it soured me on DAPs. In fact, my experience with the BTR5 and X5 has soured me on FiiO and portable audiophilia in general.