"I'm not sure how this has been 'Solved'."

The original person who asked gets to make that determination. And let's remember there was a very specific Grantor question. Not in General.

Michigan

Retail business

Working Capital; ongoing

"There could be an argument made that the proceeds are liken to Unemployment income, which is not subject to SE tax."

Not for this topic; that would be one of the other economic incentive programs. Again, without seeing the specific Grant, the "business" grants are ordinary income to the business.

"For grants that are subject to tax and reported on a 1099G, the instructions do not talk about entering the proceeds as Gross Revenue, so what's to stop anyone from reporting as other income (not subject to SE tax)."

G = a governmental unit gave the grant. Did you consider what the grant application stated? Because that's where I started. A grant to a business, to stay in business or to prevent them going out of business, is not "other income" for the business. It's supposed to be used for the business expenses, which is why they applied for the grant.

"Honestly, I'm looking for the Code, specifically - interpretations (such as mine) are great but not super helpful."

I literally copied the IRS Q&A into this topic, previously. I also provided the link to that info.

"The CARES Act established the Coronavirus Relief Fund which, among other things, appropriated $150 billion in an effort to support state governments as they attempt to provide relief to individuals and business to deal with the economic impact of the COVID-19 pandemic. Businesses may be surprised to learn, however, that these grant programs give rise to taxable income. In the case of a corporation, gross income generally does not include any contribution to the capital of the taxpayer, but there is an exception that requires an inclusion of income for any contribution by any governmental entity or civic group (other than a contribution made by a shareholder as such). Generally, most state and local jurisdictions conform to the federal treatment for income tax purposes.

https://www.withum.com/resources/what-do-coronavirus-relief-grants-mean-for-year-end-tax-bill/

The tax implications of receiving this much needed grant income can often be overlooked. Corporate taxpayers should make sure to consider the Federal, state, and local tax liabilities due on any grants received while calculating their anticipated tax liabilities for 2020."

https://www.ccsb.com/taxation-of-coronavirus-relief-fund-grants-to-households-and-small-businesses/

Small Business Grants

While grants to small businesses would appear to fit under the general welfare doctrine, the IRS has ruled that grants to a business generally do not qualify for the general welfare exclusion, because they are not based upon individual or family needs.

Congress recently changed the tax code to make clear that any contribution by a governmental entity to the corporation is taxable. Although the rule only applies to corporations, the IRS would likely treat other businesses (e.g., sole proprietorships, partnerships, LLCs and S corps) similarly.

On July 6, 2020, the IRS confirmed that the receipt of a government grant by a business generally is not excluded from the business’s gross income under the Code and therefore is taxable.

https://financialadvisors.com/blog/blogdetails/covid-19-related-government-grants-taxable-or-not

For example, the CARES Act established the Coronavirus Relief Fund, which gave $150 billion to state and local governments to (among other things) establish grant programs to help businesses impacted by the COVID-19 pandemic. The IRS has made clear that these state and local grants to businesses are taxable income.

State and local grants to businesses funded outside the CARES Act are also taxable income to the businesses.

Here, by contrast:

Grants for Shuttered Venue Operators Are Tax-Free
The new stimulus law also gives $15 billion to the SBA to make grants to live venue operators or promoters, theatrical producers, live performing arts organization operators, museum operators, motion picture theater operators, and talent representatives who demonstrate a 25 percent reduction in revenues due to the pandemic.

The SBA may make an initial grant of up to $10 million and a supplemental grant of up to 50 percent of the initial grant. The grants must be used for expenses such as payroll costs, rent, utilities, and personal protective equipment.

The SBA also covered 6 months of SBA loan payments for businesses, and they won't need to report this as taxable and they get to write off the interest.

Try this summary review:

Takeaways
Here are eight things to know from this article:

1. Government grants are taxable income to the recipient unless the tax law makes an exception.
2. COVID-19-related grants to individuals are tax-free under the general welfare exclusion.
3. COVID-19-related grants to businesses do not qualify as tax-free under the general welfare exclusion and are generally taxable, including state and local grants made under the CARES Act Coronavirus Relief Fund.
4. EIDL advances are not taxable, and expenses paid with such advances are tax-deductible.
5. Business in low-income areas that received EIDL advances of less than $10,000 will be able to apply for an increase in the prior advance to the $10,000 level.
6. The new law sets $20 billion for EIDL advances for businesses located in low-income areas.
7. EIDL advances will not offset PPP forgiveness, and any such prior offsets will be refunded.
8. SBA grants to shuttered venue operators are tax-free, and expenses paid with the monies are tax-deductible.

And please, do your own research, if you don't like these answers.