I know a thread about stimulus checks in the US was posted before, but the following online article discusses a bit more about receiving them if on SSDI, SSI, and other programs. Don't worry. It's not an exclusion. Also, in some cases, some who didn't receive full amounts in the first two checks might be eligible to submit claims for more. The article I read is at:

SSI, SSDI and third stimulus checks: Qualifications, when your money will arrive, more - CNET