The SharePoint Admin center has a fantastic List experience for searching across all sites and doing quick filtering.

A web part generally available like this would be great for tenants with lots of Sites, or Hub Sites with lots Sites associated (100s-1000s). A typical use case would be to add it to the Homepage of a Hub Site so users can filter over all the associated sites. Similarly could be used on the Intranet home to search across all Sites a User has access to.