Did you check your Instagram settings.

I don't use Instagram, so it took me awhile to even find notifications. Once I did it didn't seem obvious to me how I can stop these notifications from Firefox. After all, one of the options when the notifications pops up is to stop them via Firefox--at least that was my understanding. But it doens't seem to stop anything.

Firefox Browser/Mozilla isn't part of Instagram's nor does it have do notifications for Instagram. You should contact Instagram support about these notifications.

I don't use Instagram, so it took me awhile to even find notifications. Once I did it didn't seem obvious to me how I can stop these notifications from Firefox. After all, one of the options when the notifications pops up is to stop them via Firefox--at least that was my understanding. But it doens't seem to stop anything.

Are they small popups on bottom right corner? if so those were not from Firefox but from websites as you may have allowed some sites to send your web push notifications. You can revoke sites from sending you notifications.

https://support.mozilla.org/en-US/kb/push-notifications-firefox https://support.mozilla.org/en-US/kb/push-notifications-firefox#w_how-do-i-revoke-web-push-permissions-for-a-specific-site