I created a site with SharePoint that I want to external users to join; However, when I type everyone in the name in only option that appears is "Everyone except external users" I want to include external users how can I do that?
You may need to configure your tenant for it to available.
Already has been answered in this forum. Take a look at here
Set-SPOTenant -ShowEveryoneClaim $true
As a supplement, official article for your reference: