how do you enter form 1099-R if the institution that you received it from isn't listed?

You enter the Form 1099-R manually.

To enter, edit or delete a form 1099-R -

Click on Federal Taxes (Personal using Home and Business)
Click on Wages and Income (Personal Income using Home and Business)
Click on I'll choose what I work on (if shown)
Scroll down to Retirement Plans and Social Security
On IRA, 401(k), Pension Plan Withdrawals (1099-R), click the start or update button

Or enter 1099-r in the Search box located in the upper right of the program screen. Click on Jump to 1099-R

Online editions -

On the screen Did you get a 1099-R in 2024? Click on Yes

On the screen Let's import your tax info Click on Change how I enter my form
On the screen How do you want to add your 1099‑R? Click on Type it in myself

On the screen Who gave you a 1099-R? select the type of 1099-R you received and Continue

You can input your 1099-R manually.

Here is how to do this in TurboTax Online:

• Navigate to Federal > Wages & Income > IRA, 401(k), Pension Plan Withdrawals (1099-R) Add/Edit
• Add a 1099-R
• Select "Change how I enter my form"
• On the next screen, it asks "How would you like to upload your 1099-R?" Select "Type it in myself"
• Next it asks "Who gave you a 1099-R?", you can click "Financial institution or other provider" and select continue
• Now, you can input your 1099-R provider's info, and continue through the rest of the interview