The National Debt

No, they continue to buy US debt for very low rates of return. The first sign investors are worried will be failure of the Treasury to be able to sell bonds at the rate they want. Then they will have to raise the rates to attract more investors. Right now, US debt is considered the one of the safest investments in the world.

engineer-

Thank you.

It seems strange with all the bad news and with the huge amount of new debt plus rolled-over debt that must be sold each month.

Perhaps some (most?) of the debt is purchased by U.S. government-related entities.

Some, yes. I doubt most. (However, I don't actually know.)

At any rate, there are still plenty of eager buyers for the debt that is sold to the public.

As of September 2021, the U.S. national debt stood at over $28 trillion, and it continues to rise. While the national debt is a concern for citizens and policymakers, the lenders holding U.S. debt, such as foreign governments, central banks, and institutional investors, are generally not overly concerned about a default.
This is because the U.S. government has a long-standing reputation for always paying its debts, even in times of economic turmoil. The U.S. government has a history of always making timely payments and meeting its obligations to its creditors.
Moreover, U.S. Treasury bonds are considered one of the safest and most liquid assets in the world. They are highly sought after by investors seeking stability and security for their investments, which means that the demand for U.S. debt remains strong.
However, this does not mean that lenders are completely unconcerned about the national debt. Some lenders may worry about the long-term sustainability of the U.S. fiscal position and its ability to manage its debt burden over time. They may also be concerned about the impact of rising interest rates on the value of their bond holdings.

If the "Federal Reserve" were to forgive a sufficient amount of Treasury Obligations that it already owns, would that solve the problem?