I don't think it's reasonable to frame Signal as a US open source project based in the US. It requires deployed servers and they're all run by a US company. I don't see a way to set my app to point to a self hosted instance, but I'm sure there are related projects that let you. For digital sovereignty then, or just breaking in the US tech monopoly, it's just another US company, isn't it?
Since this isn't a self hosting channel, I think similar logic holds for Ente, but it does seem like you could self host that exact product.
Pop!_OS is from a US computer manufacturer so it could be framed as supporting a US tech company, but loosely hence the grey and not red or putting it in the left column.
But, I'm still massively guessing, I just don't think those examples invalidate the interpretation until the author says something