How to add /admin/people as a tab to a custom menu?
In a custom module (mymodule), create a mymodule.links.task.yml file, and add the following:

mymodule.admin_people:
  route_name: entity.user.collection
  base_route: route.of.your.custom.menu
  title: 'Tab text goes here'

Here's what each part does:

mymodule.admin_people Is the identifier of your menu tab item (the file being *.links.task.yml means its the menutab file)

route_name  is the route the tab points to, and entity.user.collection is the route that corresponds to /admin/people .

base route displays your tab on the specified route. To find the route for your view, download the Devel module, turn it on, and go to "Routes info" to get your route. Usually a view is of the format view.[view_machine_name].[view_display_id], i.e. view.myview.page_1 . Check the "advanced" section of your view's management page for the display ID.

title is the text that will go into the tab.