Any plans to expose this as args so to skip creating a config just to enable a formatter?

No, because it makes no sense to do that inside v2: a formatter is not a linter.

The formatters are related to the new commandgolangci-lint fmt.
They are "converted" as linter for convenience, but their main usage is related to this command.

https://ldez.github.io/blog/2025/03/23/golangci-lint-v2/

In v1 it was straightforward to CI-check if the code is formatted, as it worked as any other linter.

In v2 the best way I found is to use 2 commands separately,golangci-lint run and thengolangci-lint fmt --diff. Is this the way now?

The formatters must be defined inside the configuration file to be run by the commandgolangci-lint run.

https://golangci-lint.run/usage/formatters/