A minor aside- "Popover" doesn't quite work if you're regularly using Bootstrap because that means a specific thing.

https://getbootstrap.com/docs/4.1/components/popovers/

Gnome has a similar widget, also called a “popover”; most menus use them.

Logins are not a real purpose for modals. Just go to the login page, and redirect back to where you were. I'll give you confirmation yes/no modals, but that's about it.