I personally didn't find the lack of 3.5 mm jack to be as big of an issue as I thought it will be. I just attached the USB-C-to-3.5mm adapter that came in the box to the headphone cable and forgot about it.
Some phones support audio accessory mode, which is a way to reserve some pins for analog audio signals. In this case, you only need a passive adapter. There's no reason why desktop or laptops computers couldn't support it, too, but if they do, it's rare. So such an adapter is unlikely to work with a computer, and may not work with all phones.
The alternative is an active device, with its own DAC and amplifier. This is more likely to work with all your devices; I'm pretty sure I could connect my desktop computer's external USB headphone amp to my android phone and it'd just work.
I found it to be a really big issue. But i guess it is about expectations. I bought iPhone XS expecting it to be a none-issue, but it also doesn't come with a converter.