Here's the application. I have a solar pool controller located
outside a single family house that puts out 24V which will go to a
relay located in the attic. The controller is about 6 feet away from
the house, so the circuit will go from the relay in the attic, down
the outside of the house behind a pipe, but then needs to go
underground for the last 6 feet to the pool controller. Besides the
relay circuit, there will also be 4 other wires for sensors. So, I
need a 20 gauge cable with 6 or 7 conductors.

I've searched high and low online and can't find any wire that will
meet code. Everything that is CL2 or CL2X rated, eg thermostat cable
is NOT rated for direct burial. And anything that is rated for
direct burial, eg irrigation/sprinkler cable, is NOT rated CL2.
Anyone know of any such cable that is 20 or 18 gauge? And am I right,
per NEC 725 that I can't just use the sprinkler cable for the whole
run?

What are my other options? I'm thinking I could mount a small
weatherproof box on the side of the house near ground level and
transition from CL2 to sprinkler wire for the last 6 feet
underground. Or can I use the CL2 thermostat type wire and then put
it inside PVC conduit for the underground run avoiding the splice?
Is there a flexible PVC I could run, like is flextight allowed
underground for low voltage?

This has to pass electrical inspection as other work is being done
too.

And this got me thinking. All the irrigation installs I've seen just
use irrigation cable that is not CL rated and yet they bring it inside
garages, basements, etc. That would seem to be a technical violation
of NEC 725, no? Do they just get away with it because it's a short
run and/or there is no electrical inspection done?