Node 20 is gone from GitHub Actions runners, and so is the opt-out

Runners now execute JavaScript actions on Node 24, and ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION no longer works.⁴ If you maintain a JavaScript action, set runs.using: node24 and cut a release; if you consume one, move to a version that supports Node 24. Self-hosted runners on macOS 13.4 or earlier, or on ARM32, are no longer supported.

Relevant to: Anyone pinning an old third-party action by SHA, or running self-hosted runners on older Macs or ARM32 boards.