I do hope Eben Upton weighs in on this, because whoever signed this off, it's a bad decision all round. Blaming trademark law is just a dishonest get-out-of-jail-free that big corporations use to justify belligerent bad-faith dealing. I hope the Raspberry Pi Foundation can show that it's different. This is not a good start.
They have also replied indicating something to this effect. https://twitter.com/Raspberry_Pi/status/1318494942478635009
"This letter was automatically sent to"
I suppose they could’ve done it with a little less ‘ultimatum’, but it looks like they _did_ reach out before unleashing anything else.
This is a letter from the foundation. I don't see any lawyers listed anywhere, and no indication that they have taken legal action.