I would sample a few universities. First, a typical state school like Arizona State University, or Penn State University. Take their curriculum and spreadsheet it out.
Then, take a look at some more higher-tier universities. Could be UC Berkeley, Stanford, or MIT. Note down their curriculum in your spreadsheet.
Then, try to sample a European university, or Turkish university (MET maybe). Note down their curriculum.
Between the 2-3 samples you have, look for non-negotiable courses you must take. This is typically the courses that are common among all of them. From there, you can filter for further electives that are available, or other courses that may be more "with the times" so to speak.
This way - you can start hammering away by selecting Textbooks, MOOCs, and other online coursework that could be open-source or paid, and work your way through it.
This would be my approach if I wanted to do it completely for free, without any paper or substantial evidence that I am educated at the end of the journey. Regardless, this approach will surely help you when it comes time to actually pay for the education - you can fly through it with ease.
Also, don't ignore hands-on soldering projects, FPGA projects, or other digital logic projects to supplement your theory. They're fun and can add a lot of context. Even something simple like overclocking computers and writing some C++ projects can be a great supplement.
Food for thought, hope it helps.