I think I will push the modified source of the MonoGame.Framework to the repo, so you can modify it for your own custom build as you wish.
But I currently don’t know when I have time for it. Maybe during this weekend.
Yeah, this don’t work like this in MonoGame.Forms. You would need to set the render target back to the SwapChainRenderTarget: GraphicsDevice.SetRenderTarget(SwapChainRenderTarget)
You can generally find alot of hints/examples/explanations in the wiki:
Like for your problem:
There is also a RenderTargetManager, which simplifies work like that:
Class: Home · BlizzCrafter/MonoGame.Forms Wiki · GitHub
Create: https://github.com/sqrMin1/MonoGame.Forms/blob/master/MonoGame.Forms.DX/Services/GFXService.cs#L395
Sample: Home · BlizzCrafter/MonoGame.Forms Wiki · GitHub