I'm currently working on transplanting components onto a frame here at the shop

The replaceable derailleur hanger that came with the frameset
turned out to be direct-mount style only.
I'll sort this out later, so it's not a big deal,
but about this replaceable hanger...


This is a different frame, but the part where Puchi Kuwari-san is positioned
is part of a current Shimano rear derailleur.


↑With direct-mount style, this part becomes integrated into the frame,
so when mounting this rear derailleur on that kind of frame,
you end up using only from the pivot point onward in the left image above.


Of course, if you mount a conventional rear derailleur on
a direct-mount rear end, the angle and position become completely wrong.


So if you install a Wolf Tooth Road Link (→here)...


It gets even more wrong. Don't do it.

Speaking of which, recently Tni (Japanese parts brand) has released something equivalent to this Road Link
called the "Rear Derailleur Extender."
If you don't care about brands, think Wolf Tooth is a bit pricey and want something cheaper,
or can't get Wolf Tooth easily anyway,
I recommend it(shameless plug).

I write "rear derailleur" in the title and throughout this post as a casual choice,
but Tni's "Rear Derailleur Extender" follows the distributor's original terminology.
Incidentally, Shimano, Campagnolo, and SRAM all
use "rear derailleur" in their official Japanese documentation.