Design includes two chain links: one closed, one open with latch (carabiner). Hexagonal cross-section.
Many 3d-printable chains are designed in one p...iece, with all links already linked. While this is a nice application of "the impossible", such chains are not very robust due to the disadvantageous slicing. In addition there are long overhanging parts, which don't look very nice.
The chain of this design is less sophisticated for printing, the links are very strong and look very nice. However it needs to be assembled manually. 48 links result into a chain with 1m length. Only every other link needs to be a latching links, while the rest is closed. I've printed it on my UM2 with PETG (but I guess PLA or ABS works as well).