Is it the new norm for employers to contact job applicants via email for interviews?

No this is not normal & is a red flag. I have had that happen to me a few times where the HR person wants me to come in for an interview and either I never hear back, or I get there and the situation is totally crazy. I have some other instances but I think you get the point... when they contact you via email it's generally not good. I think it's also a sign that they are doing m emails and just doing open interviews and whoever shows up, shows up... really impersonal & unprofessional.