Bumping this thread for people coming here through search.
Another way to solve it is to enable mipmap generation and filtering for the render target. Not super straightforward and can be quite expensive, but is more flexible than stereo layers. Also I couldn’t use stereo layers because they are currently bugged for me and several other people.
I made a note on enabling mipmaps and filtering for UMG widgets here (also available as a plugin on github):