Greasy Fork is available in English.
Blocks a specific request to maintain anonymity while viewing Instagram stories.
< Feedback on Instagram Anonymous Story Viewer
Edit: it seems to still work in latest Edge 125
Yeah I only tested it on Chrome, I'll see if I can adapt it for Firefox when I have some free time. Thank you for bringing it up.
Doesn't work anymore (tested in latest Firefox 126 with ViolentMonkey)