Is it rude to use tracking softwares for the emails that you send to potential advisors?
My sense is that the vast majority would not notice one way or another but that some potential advisors might and would find it intrusive and and inappropriate. In many other cases, (like myself) professors use text-based email clients or systems that that block this kind of tracking. In these cases, folks won't think you're rude but you still won't know if I've read it. For that matter, I may have opened an email but not read it carefully. In some cases, people will notice and and think it is rude or unethical.

Critically though, I can't see why knowing whether your email was opened will help.

The reality is that many professors receive between dozens and thousands (really!) of emails from prospective students. This has been discussed at length. Many answers on this site explain why it's just not possible for everybody to reply to every email and there are many reasons why people do not. They might not reply because they are overwhelmed by teaching. They might not reply because it's simply not a good match. They might not reply because they don't have funding to take on new students this year.

My advice is to pick a small number of perfect potential supervisors. Read their papers. Write emails that make it clear that you're not just mass-emailing anybody you can find but that you want to work with them. Send an email. If you want, send a follow-up after a week or so. In either case, I don't see how knowing that the email has been opened helps.