You can't update bios from Linux. You can however update bios using F7 method or performing Bios recovery from Power Button Menu or with Yellow Security Jumper removed: https://www.intel.com/content/www/us/en/support/articles/000005636/mini-pcs.html
In the table you will see also links to two other possibilities that can work: UEFI bios update and iFlash Bios update. I prefer to use the F7 method or Bios recovery method.
You can always choose to instead purchase enterprise-level NUCs, which support AMT and remote console access. There are a number of board- and kit- level products supporting these capabilities: NUC5i5MYBE/NUC5i5MYHE/NUC5i5MYKE, NUC7i5DNBE/NUC7i5DNHE/NUC7i5DNKE or NUC7i7DNBE/NUC7i7DNHE/NUC7i7DNKE. These are more expensive, of course (manageability, especially remote manageability, is certainly not free).