See https://github.com/web-platform-dx/web-features/blob/main/features/text-autospace.yml.dist
which says the feature is not supported, anywhere.

However, the Baseline banner at the top of https://developer.mozilla.org/en-US/docs/Web/CSS/text-autospace says that the feature is available everywhere but Firefox.

Perhaps we should pin this feature to a key that's supported like what's shown on MDN, and create another feature for the rest.