The spec-compliant-ruleset at https://github.com/Redocly/redocly-cli-cookbook/tree/main/rulesets/spec-compliant (introduced in #12) looks really useful.
One thing it seems to be missing is saying which version of the spec it aims to comply with.
The explanation links for each rule point to the latest URLs of the spec (https://spec.openapis.org/oas/latest.html). This is currently v3.0.2. But at the time of PR creation, the current version of the spec was 3.1.0 (https://spec.openapis.org/oas/v3.1.0.html).