You don't need a tab suspender; You need a tab manager (partizion.io)

The great suspender was removed by google because it was sold to a nefarious buyer and then malicious scripts were implemented. We must be wary of "free" extensions and apps. Partizion is an alternative to The Great Suspender except it is a tab manager, not a tab suspender.

What are the recommended equivalents for Firefox?

good discussion, though i still think tab suspension is best.