Waiting to complete first backup

I've migrated to a my new Macbook Pro 14 inch M1 Pro, 32GB, 4 TB using the Migration Assistant.

Afterwards, I created a new backup on my Western Digital 8TB external drive. All good.

After experiencing some issues with Alfred (off topic), I decided to do a clean install of my Macbook.

Afterwards, I erased the 8TB drive and tried to create a new backup using Time Machine.

Time Machine says: 'Waiting to complete first backup'. It is stuck.

I've found an article on it here:

https://www.macrumors.com/2021/12/08/time-machine-initial-backup-error/

Any news on this issue? How to resolve it?