how the hell do you do backend focused projects for a portfolio??? i feel so uninspired compared to my ideas for showing of frontend skills. backend stuff is just not as flashy by nature, how the hell do I "show off"? my backend chops??? 0_0

Metrics, data, samples. Things that matter. If you're not a designer the shininess is irrelevant.

The one idea that comes to mind is motion graphics in a video or interactive website. In a way that illustrates how your invisible system is delivering value to it's customers.

Think www.prezi.com and something like Adobe Animate or https://tumult.com/hype/
Tumult Hype. Or animated svg. Write up your "commercial" story and get help from a graphic designer to turn it into reality.
And remember always think "what's in it for the employer".

Code samples, github projects, blog like details per project, be "creative" 😅

Previously I have just made an API to the Backend, and use a basic shiny template front-end to show off the backends capabilities.

At the end of the day, your portfolio will hit recruitment/HR staff first and foremost, you can't wow non-techs with simple data.