It's most likely BetterZip or Keka or perhaps any of the cloud syncing services.. in my case it was always BetterZip that was and still is the culprit - Look in System Preferences for Extensions and then Finder Extensions
Also, if you're using TotalFinder then take a look at what ever it does to the sidebar..
But more than likely it's BetterZip (if installed at all on your Mac)
Hi Allan,
this is probably a general problem of the whole Finder extension system as other extensions experience it too.
The only way to avoid this at the moment is to disable the BetterZip extension. Sorry for not having a real solution the moment, but I’ll keep an eye on this.
— Robert
Hi, I just posted about having the same issue you've got displayed in your sidebar with a solution. TLDR I had to update Keka.The author of BetterZip on the 15th of September 2020 wrote this in a reply to me where I asked about an issue with sidebar icons turning into folder icons when these two bottom ones are in fact external disk drives.
View attachment 2177140
It hasn't been fixed. I think Keka might be alright acting on the sidebar, but I wouldn't count on it.