I use a Make automation so that every post is added to a Google sheet. You specify what link you want to DM on the sheet. If anyone comments on that page, it reads the sheet and sends the link you provided after responding to the user. Simply signup, click the links and select "Use scenario" and connect your IG account.
Prerequisites:
a. (Affiliate) Signup for Make Automation:
STEP 1 - Import IG to Sheets automation:
STEP 2 - Import IG Auto Comment automation:
**Connect Facebook/IG Accounts
STEP 4 - Follow instructions to active IAM: