If you cannot find the 6.6.0 installer but need to work on reports for a server running that version, you can use a newer Studio version and adjust the Compatibility Open Jaspersoft Studio. Navigate to Preferences Jaspersoft Studio Compatibility Manage JasperReports Versions
If you cannot locate the official package, consider these last-resort options: download jaspersoft studio 6.6.0
There is no native Apple Silicon (M1/M2/M3) version for 6.6.0. macOS users will need Rosetta 2. If you cannot find the 6