Or I can just not do stupid shit and listen to hifi headphones released in the past 2-3 years, many of which have a 3.5mm jack (and adapters for larger, if plugging into dac/pre-amps).

Which you said aren't being made anymore. Which is factually untrue. The best bit is, they're still being made! And there's plenty of people who are still buying them!

Why? Because a $170 pair of closed-backs sounds infinitely better than the $550 Bose Quiet Comfort Ultra nonsense.

FiiO FT1 32Ω being a prime example, if you are looking for closed back suggestions :^)