Taxpayer Advocate Service
https://www.taxpayeradvocate.irs.gov/contact-us/submit-a-request-for-assistance/
While TAS primarily focuses on resolving problems related to IRS actions, such as collection issues or disputes, they can provide assistance and guidance to taxpayers who are considering or in the process of filing an OIC. TAS can help ensure that the taxpayer's rights are protected and that the OIC process is handled fairly.
Keep in mind that TAS does not have the authority to approve or deny OIC applications; that decision rests with the IRS. However, TAS can help facilitate communication between the taxpayer and the IRS and provide assistance throughout the OIC application process.
Low Income Taxpayer Clinics (LITC) assist low income individuals who have a tax dispute with the IRS, and provide education and outreach to individuals who speak English as a second language (ESL).
https://www.irs.gov/advocate/low-income-taxpayer-clinics
AARP
Get Help with Free Tax Assistance
Since 1968, AARP Foundation Tax-Aide has provided free tax help to over 75 million taxpayers, with a focus on older adults with low to moderate income. Tax-Aide volunteers are located nationwide, and are trained and IRS-certified every year to make sure they know about and understand the latest changes and additions to the tax code.
https://www.aarp.org/money/taxes/aarp_taxaide/