There’s some hope at last! TailwindLSP received a PR to fix some dynamic registration recently and that has gotten it working in Nova 
Haven’t tested this beyond the initial validation shown in the screenshot below, but I am hopeful.
The completion docs doesn’t show parse the markdown code block, but that’s minor compared to the LSP not working at all.
No promises on when/if I’ll have a chance to create a full extension, but the POC at the GitHub repo linked above is up to date.
