If I filed my 2019 Federal tax return on June 2021 by mail. I never received or heard anything from IRS. 5 months so far. I would appreciate any advice. Thank you.?

It is taking the IRS a very long time -- often more than six months --- to process mailed returns.   Unless you used a mailing service to track it you will not know when the IRS received it.   They do not post information about 2019 returns on the refund site--only 2020.   So really all you can do is wait.  

Keep tabs on the progress (or lack thereof) of the return on the IRS website using your account :  

https://www.irs.gov/payments/view-your-tax-account

Thank you 

Thank you much