Issue with Google Index checker - one of our vendors that checks whether the website is indexed by Google is facing downtime. Due to this the domains are not being checked for indexation. As soon as they fix this, we will remove the message. Sorry about this.
None of the metrics are infallible. They can all be manipulated. However, it's tougher to manipulate them all. So the ideal way is to use all the metrics together. If a domain has a high Trust Flo, but a low Domain Authority, you should research some more into it. The same goes with Ahrefs Domain Rating. The SEMrush Rank & SimilarWeb metrics should be used only for domains with organic traffic.