Can a ex felon get a grant to open a business

Probably.

It will depend on how motivated you are to find grants and apply for them and how well you can and will present yourself and your business plan to those who make the decisions.

No, there are no grants for felons. I don't think there are any grants for people who never even got a parking ticket.
You can apply for a SBA loan. But you need money and a good business plan to even be considered.
Most new businesses fail, so no one is going to even loan money very readily.

There are really no grants for business start ups. There are some that help with tax help, or low income property (if you are going to employ 100's of people)
But you will have to already have lots of funds to fund most of the business.

Grants because you are a felon or if you are a felon. No special grants for anyone today, at least not a start up.