I think everyone would appreciate if these people using LLMs to spit out these PRs would fork things and "contribute" to those forks instead.

It's a fairly simple matter to reject a PR. And a nice-to-have if they update their contribution guidelines to reflect their preferences.

It's also a fairly simple matter to respect the time of the maintainers of software you want to contribute to - by, for example, talking to them before dumping 16,000 LoC in a PR and expecting them to review it.

Unless, of course, it has nothing to do with actually contributing and improving software.