Does destroying a virus envelope make the virus inactive?
Enveloped RNA viruses will get inactivated quickly without a membrane. RNase is a ubiquitous enzyme that would quickly digest any exposed genetic material.
Via https://www.neb.com/tools-and-resources/usage-guidelines/avoiding-ribonuclease-contamination:

RNases are found in all cell types and organisms from prokaryotes to eukaryotes. These enzymes generally have very high specific activity, meaning tiny amounts of contamination in an RNA sample is sufficient to destroy the RNA. The major sources of RNase contamination in a typical laboratory include:

Aqueous solutions, reagents used in experiments
Environmental exposure, RNases are in the air, most surfaces and dust
Human contact with hands and skin


Without a membrane (and any associated receptor-binding proteins), the genetic material of an enveloped virus would not normally have a way to get incorporated into and infect the host cell, in any case.
Your question is about enveloped viruses, specifically, but there is an interesting exception of a kind, so-called viroids that infect plant cells. These have no capsid or protein envelope, but are still infectious.