IMO running a promotion is not a UDAAP issue (so long as everyone receives the discount you stated they would receive).
Why do they just want to provide the credit to online apps? That may be problematic. You're promotion would adversely affect borrowers who do not have/use the internet (LMI, Elderly, etc.). Just my opinion but I wouldn't recommend doing that.
If you run a promotion, everyone gets the deal.
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The opinions expressed are mine, do not represent the opinions of my employer, and they are not to be taken as legal advice.