Good or bad?Answered
If my high school doesn't offer extracurricular opportunities e.g. no sports program, should I mention it in an essay or additional info? Do you think admission officers would view my it in a wrong way?
I for sure think you are supposed to inform colleges about your school's lack of opportunities, and while doing that, it would be a great thing to put something that you have done for yourself and by yourself, as an extracurricular activity. Maybe you joined a race or an online group to as easy as a habit that you love to spend your time on like reading, helping around the house, creating things, hiking, or even participating in Church, Mosque, Synagogue, etc. These things show colleges you are a bright student who overcame the lack of your school with your own choices and made it a good fit in your schedule for him/herself without being stopped by your school lack of activities which, will be a positive outcome more than a negative one because colleges take into consideration the schools that students came from and what they had offered their student. And the question that colleges mostly ask about is what did that student's high school offer him/her and how did he/she take advantage of it?
Don't mention in essay, but additional info, unless you started a club or extracurricular oppurtunity that did not involve the school