I cannot accept this premise. If I purchase a three year licence from a supplier, the vendor must continue to supply the service until the end of the contract period or cancel the licence and provide a refund. To refuse to provide the service or refund the licence fee, implies that the vendor is in breach of contract, and I am sure that this would apply in Slovak courts as well as the UK courts.
I live in the UK and, as this is a "Home" licence, for me as an individual, the Consumer Rights Act 2015 must apply. The Act applies to terms in consumer contracts between traders and consumers and covers unfair terms and conditions. I am quoting from the guidance issued by the Competitions and Markets Authority. See Unfair contract terms guidance: Draft for consultation (publishing.service.gov.uk).
Am I likely to pursue this in the courts - no, it would cost too much. Will I take my business to another provider when the licence period ends - yes. Will I refer this to the Competitions and Markets Authority as a matter of principle - probably. ESET should consider more carefully how it treats its customers.