There is no Oregon "self-employment tax".

"Self-employment tax" is the employer's and the employee's share of Social Security and Medicare, both federal taxes. 

Oregon will tax your self-employment earnings (already included in your Federal AGI) but does not have a state "self-employment tax"

I have a similar question. Turbotax asks what amount of my federal self employment tax is deductible for Oregon, and asks me to enter the number. Any way to find out? It references Schedule 1 line 14.

TurboTax should automatically populate that box.  If it doesn't, you find the number to enter on the Federal Schedule 1, line 14.