Any method to add a Notification message on top of Modern SharePoint site home page

[robinrbn]

Hi Folks,

I am performing an Office 365 tenant to tenant migration. As per our plan, during SharePoint Online migration a banner will be shown in the source SPO sites notifying the users regarding the ongoing migration. For classic sites, we are deploying custom actions and it's working fine. But for modern sites, since that won't work, is there any other methods to do this? I am aware about using SPFx for this purpose, but I was looking for any simpler methods to add a message on top of Modern site Home pages.

Thank You.

[#2]

The only choice you have to show a banner in all the site in modern is by means of a SPFx Extension

[#3]

I was hoping there might be any workaround that can be done to  achieve this. Anyway, thank you for the reply @Juan Carlos González Martín .