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Ifixit gives fairphone 5 a 10/10 on repairability and maintanence
(www.ifixit.com)
This is a most excellent place for technology news and articles.
Adapters are literally <5 USD including shipping on AliExpress. At that point it's not about the price if you're buying a phone anyways, because the cheap phones haven't abandoned the aux jack.
Also the digital usb adapters should work on any phone (and computer), unlike the "dumb" ones that trigger the DAC inside the phone (if there is one).