We've talked a lot about Intuit Admin User Account Management in QuickBooks Desktop, but recently there has been a a change to the User Management involving the Admin user for QuickBooks Online. Intuit has replaced the "Master Admin" user with "Primary Admin" user in support of their mission priorities of diversity, equity and inclusion.
The new "Primary Admin" terminology has already been updated in the QuickBooks Online "Manage users' section as can be seen in my own demo-account below. There are no functional changes associated with either permissions or the users' experience as a result of this terminology change.
Note the 'Primary Admin' (Green box) reflected within the User Type (Red box) of the Manage Users function of QuickBooks Online.
QBO_Manage-Users-change_Feb-2021
Intuit's intent is to make this change across their entire ecosystem anywhere the term "Master Admin" was being used.