You do NOT need to avoid calcium foods while taking the Big 3 - using the Drugs.com Interaction Checker (https://www.drugs.com/drug_interactions.html) I entered Arithromycin, Ethambutol and Rifampin.

The NIH document cited by @blm1007blm1007 was a good general explanation of using antibiotics, but since we take the "Big 3" in combination and for a long time, it is good to know the specific requirements for each medication.
Here is what I found.
Rifampin There were no cautions to avoid calcium, but there is a list of a few foods to avoid. And a caution to take it one hour before or two hours after a meal.

Azithromycin There were no cautions about specific foods. Mixed results regarding use of aluminum containing antacids. Recommended taking one hour before or two hours after a meal. (Mixed results with current macrolide study. https://pmc.ncbi.nlm.nih.gov/articles/PMC11531826/)

Ethambutol Take with food to avoid stomach irritation. Do not use aluminum containing antacids within 4 hours of dosage.

I am still looking for the research-based dietary restrictions. Of course if one is allergic to certain foods, they should be avoided, and a healthy diet is always a good idea.

One long-held belief is that dairy products thicken mucus, and should thus be avoided by people with mucus producing conditions. According to Dr Pamela McShane, that theory is more folk medicine than reality. So unless you are lactose intolerant or allergic to milk, enjoy it!

But there are few, if any absolutes. I lost my taste for coffee while on the Big 3, but soon after I resumed drinking my mug of cafe con leche every morning, and do have the occasional second or third cup - but my essential tremor reminds me to avoid doing so very often. Also, avoiding alcohol is a sound precaution because both it and rifampin are hard on the liver.