My fed. return was ~$19k, but IRS only sent ~$6k. IRS return tracking site says $6k number is the amt of my return, but to log into IRS site, I enter ed$19k number.)

Your log on information on the IRS tax refund status website has to be exactly what is was on the original 2020 tax return that was filed and Accepted by the IRS.

Go to this IRS website for federal tax refund FAQ's - https://www.irs.gov/refunds/tax-season-refund-frequently-asked-questions

Why is my refund different than the amount on the tax return I filed? 

All or part of your refund may have been used (offset) to pay off past-due federal tax, state income tax, state unemployment compensation debts, child support, spousal support, or other federal nontax debts, such as student loans. To find out if you may have an offset or if you have questions about an offset, contact the agency to which you owe the debt.

We also may have changed your refund amount because we made changes to your tax return. This may include corrections to any incorrect Recovery Rebate Credit amount. You’ll get a notice explaining the changes. Where’s My Refund? will reflect the reasons for the refund offset when it relates to a change in your tax return.

Tax Topic 203, Refund Offsets for Unpaid Child Support, Certain Federal and State Debts, and Unemployment Compensation Debts has more information about refund offsets.

in 2 to 3 weeks you should get a letter of explanation from the IRS.