I would recommend looking at the certs listed for the jobs you're seeking. I work in development but I briefly considered linux administration and study certs for funsies. LPIC is pretty common (LPIC-1 is the only one I studied but the material is easy/boring for someone with experience). RedHat, particularly RHCE and RHCSA, is a big one but it's a lot of material and you might not need it if you're going for entry level. I can't find anything about "AWS Cloud Fundamentals" but I did waste some time on AWS Cloud Practitioner, which is actually intended for non-technical roles, so if you'd like to continue pursuing AWS work I'd recommend moving to the next cert for whatever path you're going for. Somewhat unrelated but if you want to formalize your networking knowledge, the CCNA is a fun and recognized thing to study. I wouldn't recommend compTIA. There are also subreddits for various certs with really supportive communities that also post free study materials. Good luck with your journey!