Server folder drag feedback doesn't work in firefox 89.0

Hello,

I am using the discord web app, and dragging servers doesn't give me the feedback that I see e.g. here..

https://support.discord.com/hc/article_attachments/360033987691/5.gif

NOTE: image from https://support.discord.com/hc/en-us/articles/360030853132-Server-Folders-101

What I see is..

https://media.giphy.com/media/nNHBOlS2BTtM3g7O6o/giphy.gif 

My OS is..

Linux Mint 20.1