The two most common methods is to moisten scrape and putty coat the lid or encapsulate with 1/2" sheet rock and finish. There are arguments for both techniques . Some older homes have asbestos in in acoustical material that can be expensive to remove therefore encapsulating is best. Have it tested. Some acoustical is cement plaster based and very difficult to scrape also a good reason to encapsulate. I would contact a quality drywall contractor in your area for which method is best for your particular condition.

Ceilings are sloped in the dr and kt - about 9 ft in the living room. We are renovating - as you can see!

Call in a drywall company - look for recommendations. This does not appear to be an older home. I doubt you want to get into renting scaffolds to get up to the ceiling.

The process for removing a popcorn ceiling is very messy. Type in How to remove a popcorn ceiling in web search and the information is there.

Thanks to all for your input.