Greasy Fork is available in English.
在Instagram页面加入下载按钮与开启按钮，透过这些按钮可以下载或开启大头贴与贴文、限时动态、Highlight中的照片或影片
try downgrading to 1.17.3 that one worked for me.
Except for the saved post, it works on my PC with Firefox (114.0.1).
So it's hard to debug from my site, but I think 1.17.3 working is an important clue. I will try to address this by comparing 1.17.3 and 1.17.4.
[14/JUN/23-21:12] Version 1.17.4 It's not functioning properly on Firefox. The icons have vanished from the main newsfeed as well as from photo or video posts. The only functioning feature is the download option in the stories.
Firefox 114.0.1 (64-bit) | Windows 11 Pro x64 [OS Build 22021.1848]
(P.s.: It works fine on Chromium based browsers)