找到个插件，https://addons.mozilla.org/en-US/firefox/addon/redisposition/
ReDisposition，但是Not compatible with Firefox QuantumNot compatible with Firefox Quantum
且https://github.com/muzuiget/redisposition中说
Note: Because Firefox 57 will drop support legacy add-ons, and I don't had any time to migrate it to WebExtensions yet, this project is in maintain mode, bugfix only, no new feature.
最后好不容易找到了这个‘下载文件名编码“插件
https://addons.mozilla.org/zh-CN/firefox/addon/download-filename-encoding/?src=api
解决了下载中文文件名乱码的问题。
ubuntu就是不断地遇到各种各样的问题，sigh