An employer is not entitled to know an employee’s diagnosis, they can ask about: the expected length of their illness or disability.
Some employers may be hesitant to accept virtual medical notes or notes from telemedicine providers. However, it’s essential to consider the evolving nature of healthcare, especially in light of the COVID-19 pandemic. Many healthcare providers have adapted to providing virtual care, and virtual medical notes may be just as valid as traditional ones. Discriminating against virtual medical notes may be problematic if they are legally valid and meet the necessary requirements.

Compliance Briefing: Are You Allowed to Ask Sick Employees for a Doctor’s Note?
Doctor’s Note Policy
Solving the “Self Serving” Medical Notes Puzzle