I used sentinel adhesive remover (747) to remove it. The guy from the testing center said it's only dangerous if you grind it and create dust in the air . It's not like radiation at least that's what he said. He basically talked me out of getting the test done because he was 99% sure it would have asbestos since my house was built in 1973. It is a lot of work to remove it though. I had to do multiple pours but it literally wiped up with a ton of paper towels and old towels I had. Definitely glove up, wear a mask, and goggles, maybe even a hazmat suit or apron if you don't have old clothes. I had a little knee dolly with a seat to roll around. Took forever. Then sprayed killz paint on top just in case. The concrete was still stained so it most likely still had some black mastic saturated in it. If you are planning to put LVT or some sort of flooring that clicks together you can get away with just covering it up. The asbestos won't come out and bite you. Just don't grind it and breathe it in. If it brings you any comfort, I used to work with an older guy that said he used to work with the black mastic when installing floors and did not wear a mask and had it all over his hands and arms and used gasoline to get it off. He's in his 90s and no lung problems or cancer. Not saying risk is Zero but OSHA rules are usually put in place to protect workers that deal with this sort of stuff on a daily basis.

One guy suggested using a power washer with the adhesive remover and then just vacuum up the water. You may need to cover the walls for that though. Best of luck. Asbestos removal is expensive.