Whirlpool LGR5636PQO
Cleaned exhaust; good air flow
Replaced igniter and flame sensor
Still no flame?
Please advise next items to check or replace

Check the gas valve coils. Usually they are the culprit. I don't know what they should measure (ohms) when they are good, but when we can't get ignition on a gas dryer, that's usually what the problem is. Measure the resistance of the new ones and write all the numbers inside the dryer on the sheet metal somewhere. A Sharpie works well. Then you will know it the next time you have problems.