I think, it's not known well in the space, because the target audience is either interested in "comes from Microsoft, with support", "i want an audit-able solution, shared-source, or open-source", "is installable through my normal package sources", "something i can build/setup/cluster/manage myself". Thinlinc (iiuc) is none of those. Please correct me, if my info is inaccurate/outdated.

Hum, well it doesn't come from Microsoft but I believe it has paid support, and it is auditable, like you can setup access logs and all that, and it has an admin interface and can be self hosted managed with an admin interface and all that jazz. You can setup a cluster of them as well, I think their main business are schools and such. Though yes, it is closed source (for the most part, since it uses TigerVNC under the hood and ssh I think, so it's partially open source in that sense). And ya you need to install it with their installer.

But I just use it for personal remote desktop, I have a cloud instance and I remote to it for my dev work, while my laptop runs windows. I find it's better than say trying to use WSL.