The Trump administration just filed a brief with the Supreme Court calling for the ACA to be overturned. The president has not proposed a replacement plan. Trying to repeal the ACA, along with the response to COVID-19, will define President Trump on health care in the election.
Here is the Trump administration's brief filed with the Supreme Court arguing that the entire ACA should be overturned, including pre-existing condition protections, premium subsidies, and the Medicaid expansion.
https://www.supremecourt.gov/DocketPDF/19/19-840/146406/20200625205555069_19-840bsUnitedStates.pdf
https://www.supremecourt.gov/DocketPDF/19/19-840/146406/20200625205555069_19-840bsUnitedStates.pdf
Overturning the ACA, as the Trump administration is arguing before the Supreme Court, would affect virtually every American in some way, in the midst of public health and economic crises. https://www.kff.org/health-reform/fact-sheet/potential-impact-of-texas-v-u-s-decision-on-key-provisions-of-the-affordable-care-act/
If you want to understand the lawsuit to overturn the ACA before the Supreme Court, @mmusumec has you covered. https://www.kff.org/health-reform/issue-brief/explaining-texas-v-u-s-a-guide-to-the-case-challenging-the-aca/