NetSparkle is a C#, cross-platform, highly-configurable software update framework with pre-built UI for .NET developers compatible with .NET 4.6.2/.NET 6+, WinForms, WPF, and Avalonia; uses Ed25519 signatures. View basic usage here in the README and try the samples for yourself.
When a WinForms app uses Sparkle, the UI is blurry. Have tested a few fixes from here, but they weren't successful.
WPF-based apps are fine, even when they use the WinForms-based NetSparkle UI for update checking.
See also #44.