I closed/dissolved a single-member LLC in 2021. What forms do I need to include in my return to report this appropriately?

Did you close it or sell it? LLCS are disregarded so you don't need any forms if you closed it. You have to deal with the assets if you have any at some point.

I closed it mid-year. So there was some money that came in from services I provided prior to closing, and the remaining assets were distributed to me. 

It depends.  If you are using Turbo Tax Self-Employed, there is a question that asks if you sold or dissolved your business. 

1. Sign in to TurboTax.
2. Click on the orange Take me to my return button. Go to Income and Expenses 
3. Then go to self-employment income>self employment and expenses>start
4. Answer the questions on the screen regarding your business profile.
5. Now under general information select Stopped work in 2021 and select edit.
6. The next screen will say Tell us about how long you've worked in XXXX.
7. Here you will indicate I stopped XXXX in 2021.
8. Continue answering questions in this section until you are done with the section.

Thank you, Dave!