Unlike the sanders, the Festool TS55xxx works fine with unlimited dust extraction, such as from a shop vac. The vac end of Festool 27mm and 36mm hoses fits in the International Standard shop vac connector.
However, this does not mean that you will be satisfied with the dust collection with your TS55REQ by simply hooking up a 27mm or 36mm hose to your shop dust collection system. Shop and Festool vacs designed to use hoses of 50mm or smaller pull a relatively small volume of air at fairly high velocity. Contrast that with the dust collection systems which consider 100mm dia hoses to be small. The DC systems are designed to move vast quantities of air at relative low velocity.
Certainly we all have our personal standards of what constitutes acceptable dust extraction. Maybe for you using an adapter to hook the nominal 50mm vac end of a Festool hose your shop DC will for you be satisfactory. It will for sure be better dust collection than not connecting the TS55REQ to any collection.