And whereas your second point supports the notion that not having a jack may not be sustainable in the eyes of the OP, some earbuds seem to be up to having the battery changed.
There’s also an iFixit guide to a Samsung replacement
Anyone with a wireless headset will be fine with the FP4 and presumably tied into the battery issue.
Let’s hope the Fairphone earbuds are more than sourced as fair as possible but are easy enough to open and swap batteries