For collectors and hobbyists, the original membrane keyboards on Sinclair machines are notoriously prone to failure. The ZX-Key's "hub" approach solves two problems at once: it provides a for the original machine and a way to maintain tactile authenticity when moving between a real ZX81 and a modern PC emulator.
Always back up your software ZX Hub Key in a password manager. If you lose the physical dongle, recovery may require a factory reset of the entire hub, erasing all paired devices. ZX Hub Key