This is really the key. Grinding something you don't actually enjoy or find useful is pretty deathly, even if you get actively paid for it. "Low level", as others have said, is a very, very broad field and if you have an general interest in lower-level stuff, home in on what specifically interests you by trying to achieve some actual goal of use or interest to you.

It doesn't really matter what it is, it could be porting FeeeRTOS to your toaster, writing a kernel driver for something, reversing some device protocol, implementing something on an FPGA or building some embedded device or hacking another one into something else. Just get stuck into something and feel the gravity of your open interests.

Nothing you learn along the way will be a waste.