I know it’s not supported anymore, but I have an old project using Unity 5. I installed it through unity hub but unfortunately it stops at the splash screen forever.
I tried creating a new empty project using unity hub with Unity 5.4.1p3 and I got the same problem of stopping at splash screen. So that rules out the project as the cause for the problem.
I still keep U5 running on an old laptop just for grins, but that laptop can never be updated past MacOS Mojave.
The above looks like a Windows machine so perhaps the same thing goes for Windows? Not sure how compatible older binaries are with Windows.
As long as you have proper source control and / or backups, you might as well try installing a recent LTS version (try Unity2020 LTS first) and letting Unity upgrade anything it needs to. Unity is pretty good with its core functionality when upgrading. It’s usually all the third party crud that fails.
similar issue is where it hangs for searching license,
i think running the unity alone (instead of launching project) did open that old license activation dialog.