If I add an external guest (that does not currently have a Microsoft Account) as a member of an O365 Group, why doesn't the Sign in page have the "No account? Create one!" link? They are stuck - they don't know what they should be using because nothing on that page is saying to use a Microsoft account or create one if they don't already have it.
Even if I email the O365 group - which sends an email to all members - they'll get the email sent to them because they are members - but then if they click a link like "Add to the team site" or "share files" it brings them to the Sign in page - where there isn't any ability for them to create the necessary Microsoft account.
I swore I used to see that page you have above (the white one with the option) but all it is is the Microsoft sign in page with just the field for their username and the "Can't Access your account?" which only recovers a lost password, still no "don't have an account, create one!"
I'm lost with how it is expected to create one for someone that doesn't already have one.