Yes - while WPF and Windows Forms are still Windows-exclusive, there are several cross-platform UI libraries for .NET Core, like Eto.Forms (https://github.com/picoe/Eto) and Avalonia (https://avaloniaui.net/).
Docker is a better way to distribute apps than Electron, in my opinion. From a developer point of view you just build a regular web app, so better than Electron. From the user's point of view, Docker is better because of isolation, and because there is nothing to install. You run just one command to download and run the image. If you want the app to have its own window then use Chrome's "Create shortcut" command. This is indistinguishable from an Electron app, but better. See an app written in this fashion here: https://hub.docker.com/r/eurekasearch/eurekasearch
"From the user's point of view, Docker is better [...] run just one command"
Nope. Your "better" solution just became fundamentally impossible for 99.9% of users.
I've had to debug every install of docker for windows that I've done because it doesn't set something up correctly. Usually this involves googling the error message, finding a github thread where people are talking about which builds this affects, and then trying one of three or more powershell commands to fix whichever part of the install failed. In the most recent attempt, the error message told me to enabled virtualization in the BIOS, but it was actually that HyperV had not been enabled properly[1]. It was installed and the UI ran, but if you tried to start any VM, it would fail. I doubt debugging this sort of thing is feasible for an end user.
Docker Toolbox, although less polished, is based on VirtualBox and happily runs without Hyper-V. The only thing I've found missing is the control panel GUI.
I don't know about Eto.Forms but from what I have tried of Avalonia I'd say It could only be used for toy projects: there is almost no documentation, there are missing features like app icons, system tray, etc. Maybe in a few years It might be good, but I'd stay away from .net if the purpose is to have a cross platform GUI app