I looked up Azure hybrid benefit (using Bing..) and the first hit was MS which says
"Azure Hybrid Benefit is an Azure offer that helps organizations reduce expenses during their migration to the cloud. By providing Azure discounts on Windows and SQL Server licenses, and Linux subscriptions, it supports infrastructure modernization and a cloud-first strategy."
(key point is providing discounts, which is what my assumption was originally)
They also mention discounts for Red Hat Linux, SuSE Linux, and Nutanix, none of which of course are MS products.
I dug up the SQL server 2019 licensing doc (the version my org uses), and on page 30 it seems to indicate what I expected, specifically mentions non Azure clouds.
"In the case where you are using AHB to license your primary database running on shared hardware in the non-Azure cloud, you may run the two passive SQL Server instances (one for HA and one for DR) in a separate OSE running in the cloud on shared hardware to support failover events."
They have a chart showing 36 total cores, 12 are "active" and 24 are standby, only 12 cores are needed to be licensed. I don't know what "AHB" is that is the only mention of that term in the document. Though the version of the doc I have is copyright 2019, I found a newer version copyright 2022(page 26 on the newer doc) which changes the language for this section to be Azure cloud, but the below section remains the same.
Then below that they have another scenario with 24 cores in use, 12 active, 12 in a non Azure cloud. Only have to pay for 12 licenses.
"Primary server licenses covered with SA include support for one Disaster Recovery secondary server only (outside Azure), and any additional secondary Disaster Recovery servers must be licensed for SQL Server. Note: The rights to run a passive instance of SQL Server for failover support are not transferable to other licensed servers for purposes of providing multiple passive secondary servers to a single primary server" (which seems reasonable to me)
Pretty confusing I guess in any case..keep it simple & on prem is my strategy(though I deal with windows maybe 10% of the time) which seems to be the most cost effective/most reliable for me. Moved out of cloud in 2012 and have never looked back.(though that hasn't stopped others in the orgs from trying but then they give up when they see how much more expensive it is).
Oracle is certainly tricky to deal with too, haven't had to deal with them in a while. I do remember educating the sales/audit team back in 2007 about their own CPU licensing (specifically Standard edition had no limit on cores/socket at the time anyway which they didn't know) when the org I was at at the time was undergoing another Oracle audit.