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.

I guess the underlying assumption is that the sender is entitled to consideration and/or an answer, and so OP is trying to enforce this entitlement.

In email correspondence (academic or not), this assumption is usually wrong unless there is an established relationship (eg within a company), and trying to force it is indeed considered rude - or even intrusive/threatening.

I guess most people won't care about or notice the tracking (after all, we are OK that virtually every website tells Google about each web page we open), but if your e-mail happens to trigger an alert in their mailer or anti-virus, it won't do you any good.

It should be noted that e-mail tracking techniques are spectacularly bad at their primary purpose: reporting whether an e-mail has been read. Some people (like myself) configure their mail clients to never fetch online content, so you'll never see the notification. Other configurations may result in images being automatically downloaded, so you'll see a false positive.