I just found out that you can, in fact, charge your Ear (2024) in an Ear (a) case. So if you’re willing to pay $20 USD less, but still get the premium features, you can.
Also, the app shows the battery percentage of the Ear (a) case with just an Ear (2024) in it, just like it would with the original case.
edit:
I know this isn’t super useful for an Ear 1, sorry