Locating Java via “where java.exe” found both “C:\Program Files\OpenJDK\jdk-18\bin\java.exe” in the path (which I was expecting) and “C:\Program Files\Eclipse Foundation\jdk-8.0.302.8-hotspot\bin\java.exe” which I wasn’t. https://chocolatey.org/ recently upgraded the OpenJDK from jdk-17 to jdk-18; and at the same time this seems to have dropped behind the “unexpected” old JDK in the path. Testing with each showed that the old Java had the scaling issue but OpenJDK 18 did not, so I could just uninstall JDK 8 to fix the problem.
Had that not worked the Windows 10 compatibility settings described in the SuperUser article would presumably have worked, as would “explicitly saying which Java to run” and changing the path around so that JDK 8 was after JDK 18.