I don't use Ubuntu so I'm not entirely sure if your issue is due to the same root cause as mine, however I did report an issue with macOS Catalina subpixel antialiasing on non-Retina displays here:
Selectively enable subpixel antialiasing on macOS Catalina
A toggle to enable/disable subpixel antialiasing at the application level (e.g., as is available in iTerm2) would appear to be an useful solution to both of our issues.