Outdoor Dumb PIR linked to smartthings?

Alwas is correct - that’s a good way of doing it. Assuming you’ll be using a PIR that closes the contact when motion is detected, and then releases the contact whenever motion times out, just make sure you adjust parameter 20 to a value of ‘1’. The default ‘0’ assumes the connected switch is momentary (which it’s not) and a setting of ‘2’ would toggle state on contact change, meaning you can get the light out of sync with the input (closed = off, open = on). A setting of ‘1’ ensures that it will always be in sync, even if the light gets turned off by another means before the motion times out (or if it’s already on when motion begins)

There’s a limitation of the above approach - as far as SmartThings (or any other platform) is concerned, the only ‘device’ you have is a light. The PIR is also hard wired to the light, which means it will always operate. Another approach would be to make the PIR itself ‘smart’, that way you have 2 devices - a motion sensors and a light. This allows more complex automations, notifications etc because you’ve decoupled the two.

In order to do this, you’ll need one of these - https://www.fibaro.com/en/products/universal-binary-sensor/

Here’s the DHT for it - [RELEASE] Fibaro FGBS-001 Universal Binary Sensor (UBS)

Disclaimer - I’ve never used the Universal Binary Sensor on SmartThings. I have used it on other platforms though, and it works really well.

Another thing to bear in mind is that I believe the UBS is now technically a discontinued product. It’s being replaced by the Smart Implant https://www.fibaro.com/en/products/smart-implant/ (basically the same device, but in a case). Shouldn’t matter though, the UBS seems to still be readily available.