I think it's quite rare for linux developers to not do it on behalf of some company.

Weren't a bunch of modules deprecated recently as a consequence of intel layoffs?

> I think it's quite rare for linux developers to not do it on behalf of some company.

Corporate-sponsored contributions are probably the majority, but I don't think true volunteers are super-rare. But in both cases they're a "volunteer" from the perspective of the Linux leadership - they're contributing the changes that they want to make, they're not employees of Linux who can be directed to work on the things that that leadership thinks is important.

(And conversely it's the same with Rust - a lot of those volunteer contributors work for employers who want Rust to have some specific functionality, so they employ someone to work on that)