This isn't exactly news breaking news.
Swedish SAAB, whose fighter jet (Gripen) doesn't claim to be stealth, started selling radar systems back in 2015 based on custom-manufactured Gallium Nitride (GaN) sensors that can detect "some" "stealth" fighters.
https://saabgroup.com/media/stories/stories-listing/2015-3/l...
https://www.janes.com/article/83778/us-to-evaluate-saab-gan-... (Oct 2018)