In the style.css file of Twenty Twenty One, there is a typo on line 2873:

p { line-height: var(--wp--typography--line-height, --global--line-height-body); }

The second argument to var is clearly meant to be var(--global--line-height-body), not the bare variable name --global--line-height-body. The latter is simply an invalid value.

Normally I would file this kind of thing as a ticket or issue in the source control repository, but I couldn’t find a way to do that. I hope this gets the attention of someone who has the power to fix it!

Cheers,
Alan