How can I ask a lecturer not to disclose (my) grades publicly? In my university, some, but not all, professors upload online the grades of every student and their names next to them a few days before making them final at the end of the semester. This is done to give a chance to the students to point out any mistakes the professor may have made.

No one other than the students can see the final grades. When the professor uploads the non-final grades, they are visible by everyone.

Since few people get good grades, others are jealous of them. Long story short, I really have an issue with this.

Is it unreasonable to ask my professors to email my grades instead of uploading them online, like they do with everyone else? What other alternatives do I have?

I live in a European country.
My experience from European universities is that even there, the grades should not be posted by name, but instead by a student ID number. However, in most cases, the university requires the public posting of the grades in such a manner (for exactly the reasons you suggest—to allow for petitioning of changes in grade).

Moreover, because of the large number of students who may be taking a course, it can be highly impractical for the teaching staff to respond to individual requests for reporting grades by email. (Imagine having to send out 1800 emails for a single course!)

Consequently, while you might ask for anonymizing of the grade reports by student ID instead of name, I think it would be unfair to ask the professors to report individual grades by email, unless you have an exceptional and demonstrated need for such an email (for instance, you are unable to get your grade because of extended absence without Internet access).