Dumb q, if I install Linux and later decide to reinstall Windows, is that OEM license still good?
The answer is a resounding maybe. If you activated with a Microsoft account or if there’s a TPM chip, the chances of it still working increases. There are different kinds of licenses, but if it fails, there’s a better than not chance calling MS support and just telling them you had a hardware failure on your laptop and you need to reinstall, they’ll get you going. Not a guarantee though. And I’ll caveat and say this information is a couple years old (I don’t work in tech support anymore).
You can just reactivate by troubleshooting your activation in Windows.
No need to call Microsoft about it.