I'm using the adapter for half a year. It's bad. First of all, connection is not stable, any force applied to the connector is degrading both sides of the connection. With headphone jack phone lives happily in the pocket, no issues for like 4 or so years (upgraded phone after that to the phone without 3.5mm connector), and with usb-c it was like a week or two before some interruptions started, changing cable side is possible but does not help much.
I've tried BT too (BT DAC module), it's both much lower sound quality and still has connectivity issues as well (having your body in the way of bluetooth radiowaves somehow is enough)
Depending on your headphones, the adapter might not fit within their case.
Also, if you're like me, you have multiple headphones/earphones (the earphones always with me, since I might not have a bag to carry the headphones). Thirdly, the adapters are not universal, and thus they won't work with all your phones (I always carry two phones with me: personal and work one)