@Override
		public List<LanguageDescription> getLanguageDescriptions(
				boolean includeDeprecatedLanguages) {
			// Include deprecated languages
			List<LanguageDescription> list = new ArrayList<>();
			list.addAll(langService.getLanguageDescriptions(true));
			if (includeOldLanguages) {
				list.addAll(Arrays.asList(oldLangFactory.getLatestOldLanaguageDescriptions()));
			}
			return list;
		}
Language service which includes all languages, including old and deprecated
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/debug/GenerateOldLanguagePlugin.java