hey hey! hope all’s well 
some very good topics, which thankfully point to docs gaps more than system troubles, so hopefully this reply helps!
Crow clock input
under PARAMETERS > CLOCK, there’s a crow in div setting which determines how many clock pulses should register as a “tap” for the BPM matching. you’ll need to fine-tune to match this to your clock source’s pulses per quarter note.
so, if a clock source sends four pulses every 500ms to represent 120 BPM, then you’ll want to set crow in div to 4 to match the norns clock tempo displayed.
if fiddling with different values doesn’t give expected results, please share what your clock source is and we can investigate the specs 
i just had a dark night of the soul writing a transport into cheat codes, so i am fresh on the heels. big picture: each script needs to define what should start and stop and reset whenever these messages are received. this is a docs gap which i’m writing to fill, but essentially norns already has two script-definable transport calls: clock.transport.start() and clock.transport.stop(). these are hard-coded to respond to MIDI start/stop messages (if clock source is set to MIDI), as well as Ableton Live’s “start stop sync” (if clock source is set to Link).
so, simply put, the functionality has been present in norns for a year, but very few scripts utilize it because it wasn’t well-documented. i’m hoping that this docs effort will help clarify when to use what and why, but if you have a few scripts which you’re totally dying to have this in, let the author know and i’m totally happy to help how I can
@vicimity 's Initenere comes to mind as a script which makes use of these messages.
@artfwo can speak more to the architecture, but from what I understand the clock runs its own transport which can derive a tempo from an external source but it doesn’t wait for ticks (like ansible or other modular gear which require constant pulses to advance [if a patch cable is in their clock input]). apologies if this is a dumb question, but how do DAWs handle incoming clock swing driving their main clock?
as far as outgoing swing, @tyleretters’s lattice provides a really nice framework for scripts to incorporate swing, but this is a new library for script authors. in fact, lattice also has a nice framework for scripts to act more like modular sequencers where a pulse event is required to advance. excited for more people to use this!