I plan to have real estate investments and other alternative investments within it.

You will have to be more specific.

If you are referring to outright real estate ownership, this is a rather specialized area for IRAs and the number of custodians are quite few. There are also some limitations, such as you and your immediate family cannot reside at the property, manage it, or work for it, and it must be owned outright (IRAs cannot borrow, which means no mortgages).

More typically, people get real estate exposure in their IRAs through REIT stocks (just about any discount stock broker can be the IRA custodian) or REIT funds (just about any broker that handles the specific fund or that fund family can be the IRA custodian).

It is similar stories with "alternative investments": outright ownership in an IRA is rather specialized, stocks or funds that invest in such investments can be held by vastly far more IRA custodians.