Is an undergraduate thesis a requirement to get into grad school? I'm about to start my last term as engineering student, and my goal after I graduate is to get into grad school and pursue a master's degree in Computer Science or software development. However, my university is offering me two choices in order to opt for my degree: undergraduate thesis, or just internships (+ internship project). I already received some suggestions from colleagues that due quarantine and confinement is preferable to just go for internships, which I'm almost finishing working from home. 

Nonetheless, I'd like to keep asking for second opinions about this. Can I freely choose only my internships without worrying if that could harm my application into grad school? I'd deeply appreciate any suggestion. Thanks in advance.
No, it's not necessary. 

Of course, all other things being equal, writing a (good) undergraduate thesis can only help. It demonstrates research capability and independence, and you'll probably get a more detailed letter of recommendation than you would from a professor who you saw only in class. But a similar argument can be made for many extracurricular activities, and you don't have time to do everything.

If you choose to write a thesis, do so because you are interested in the challenge and the topic, not because you are afraid not writing one will prevent you from getting into graduate school.