How to connect bathtub drain pipe to existing floor drain?

I have this floor drain and I want to connect it to a bathtub drain so basically another pipe. The diameter is about 40mm of the narrower pipe, although it has a thick border.

It is most likely a nanhi trap so I cannot remove without breaking stuff up but it also means that I don't need another p-trap.

So my plan is to either put a more narrower pipe inside and glue it ( like a 38mm if I can find it ), or use a compression connection for PVC pipes for a standard 40mm then connect another 40mm pipe on top of it and work from there.

The third way would be just to connect it to the whole top layer pipe, but that I don't know how it would make a perfect seal.

Would you say that any of these ideas are ok and some more preferable?