> I have no idea how LWN can be sustainable, ...

Speculation: LWN is sustainable because there are enough people out there who recognize the value of such a source of information and are willing to pay for a subscription.

>... but I can assure you that it's the exception, not the norm.

Anecdata: I credit a good portion of my success to knowledge and insight I've gained from lwn articles.

If you're in a position to do so, I always recommend getting a paid membership, particularly if you've found their articles helpful to your tech journey.

(i am not affiliated with LWN, just a happy subscriber)