Is there a requirement to update Intel NUC BIOS after 4 years of successful operation?

[bearFNF]

UEFI or Legacy were options in BIOS when setting up the NUC so is already there, just depends on which one you (or whoever set it up) selected.
The link above to step 2B of rock install guide should show you how to get into the BIOS to see what you are running.
Or as Wade said check the webUi for tailscale:

I don’t know all the specifics fixes and features but, there was a bug fix for some HDMI outputs on NUCs:

RoonOS (Nucleus / ROCK) build 256 production is live! [UEFI ONLY]

Hello Everyone, This is a very small update to RoonOS which addresses a bug which prevented the HDMI port on some devices to output audio. If you have been experiencing issues with HDMI audio output then this release should get you back in business. Should you encounter and problems please don’t hesitate to let us know in the #support category. This update is only available for devices created using the UEFI boot image (build 254). There will be no legacy build available which means that this …