This is how my parents heated their house since before I was born. My father got a sheet of fireproof board 1/2" thick & fastened it to the brick around the fireplace opening, & just ran a pipe into it. Burned wood that way for decades.
As he got older, the cutting, splitting & hauling standing dead trees was getting to be too much, so he bought a Harman Mark I -- same one I used to have.
This time, it was installed to code ( inspections have become EXTREMELY strict compared to 30 years ago ) after the building inspector got my old man all fired up with pages of requirements....
He set it up the same way, only he had to continue the pipe (with stainless steel) behind the board & up the chimney, ending at the damper. He cemented the whole damper assembly closed around the 6" pipe. The inspector liked what he did & passed him ( 4th visit -- dad was NOT happy
So ... he ended up spending almost $400 extra to get this guy to sign off on the work. Such is the world we live in today......
So depending on how strict your inspectors are, you could do any variation of this same method.