Microsoft has added a new group policy in Windows 10 20H2 that allows you to disable a new feature that customizes the taskbar based on what accounts or devices you have. The Programmable Taskbar is a new cloud-based feature that will add different pinned programs. Microsoft introduced a new policy called ‘Turn off cloud optimized content’ for Windows 10 Pro and Windows 10 Home users. For those who wish to always use the default Windows 10 taskbar, Microsoft has provided ways to enable this policy.
Source: https://www.bleepingcomputer.com/news/microsoft/new-windows-10-policy-lets-you-disable-cloud-customized-taskbars/