2018 Ram EcoDiesel w/ 250k miles. Sitting at idle today after about a 30 minute drive and about 15-20 minutes at idle, and the truck just dies.
Pressed the button and it starts right up. No problems. No excessive spinning or sputtering at all. Completely normal start.
About 5 minutes later, dies again sitting at idle.
Press the button, completely normal start again.
About 2 minutes later, dies again.
Press the button, completely normal start again.
Runs for 30 seconds - 1 minute and dies again.
This time I let it sit a while and started again, no problems. Made it about 1 mile down the road to Auto Zone and died right before the parking lot. Luckily I was able to coast.
Replaced my fuel filter in the parking lot. Started up and ran idle for roughly 25-30 minutes before dying again. Let it sit for about an hour, started up and drove home about 30 minutes away. Once I got home, I let it run in the driveway for about an hour before it died again. Started it up and it ran for about 2 minutes before it died again.

I'm baffled to say the least. Any advice is greatly appreciated.

Bad fuel?

Any warning lights? I'd scan for codes and check your gas (diesel) cap as it might be due for replacement. Two easy things to start with.

No codes at all. These trucks don't have caps on the fuel tank. Very frustrating

Have you checked the battery/charging system? Doesn't seem like a fuel issue to me, sounds more electrical. Battery going south, alternator going out, bad ground etc. A couple years ago my Jetta started lighting up the dash with every warning light and occasional engine stumble but it was intermittent, a new battery solved all the issues.

This is my next step. Then the lift pump in the fuel tank.

Does it have an egr valve? I had the same issue on a hemi & it was the egr valve.

The DEF system was "put to sleep" about 50k miles ago, so all of that should be inactive.

I don't think the EGR valve is part of the DEF system.

R.I.P

Was this the one that has the High Pressure fuel pump recall?

SAFETY RECALL Z46 High Pressure Fuel Pump - 2014-2020 Jeep Grand Cherokee, & 2014-2019 Ram 1500