no headphone jack means you may need to purchase wireless headphones or earbuds and wireless earbuds don’t always have replaceable batteries
They’re also more expensive, even if fairphone does offer their own headphones.
A cheap set of decent wired earphones is $10. $30 if you want something nice, like an IEM.
Bluetooth headphones don’t tend to be quite as cheap, and are usually a good deal more.
Or shut them down, given the recent debacle with Amazon shutting down someone’s account, disabling their devices in the process.