The original author of pgBackRest posted on LinkedIn today that he will very likely revive the project, given the interest and new sponsorship opportunities: https://www.linkedin.com/feed/update/urn:li:activity:7457070...
That said, this post predates that LinkedIn post, so I don't think it was intended to compete with the original author's own efforts, but rather to provide continuity for PGX's customers.
Tried submitting that as seperate link for discussion - I'm sure many would be relieved seeing the project live on.
Unfortunately I guess hn doesn't allow LinkedIn posts?