While building, Unity just freezes on compressing stage or "Building native binary with IL2CPP". No response from task manager, 0% CPU usage. No errors. I know it takes a while but I left laptop on for 2 hours and it still was on the same stage. Sometimes restart helps, but only for 1 build.
This does sound like something new. Which OS? Which Unity version? Any chance you'd be able to pinpoint if the Build step launches a process that gets stuck and does not proceed? Do the Unity build logs give any messages? When you write "only for 1 build", do you mean that you can make one successful build per computer restart?
Can confirm. Brand new project on 2020.1.6. Building html5 freezes Unity and obliterates my cpu with max usage for quite some time. Typing this while it's still going. Always getting the feeling that Unity gets more unstable with each new update.