As a self employed person when traveling to Taiwan and China for business can you use per diem rate for meals? Or you have to show all the receipts?

Yes, you can.  Instead of keeping records of your meal expenses and deducting the actual cost, you can generally use a standard meal allowance, which varies depending on where you travel. The deduction for business meals is generally limited to 50% of the unreimbursed cost.

Per IRS:

• "Meal expenses are deductible if your business trip is overnight or long enough that you need to stop for substantial sleep or rest to properly perform your duties. Meal expenses are also deductible if the meal is business-related entertainment. You can figure all your travel meal expenses using either of the following methods:
  • Actual cost. If you use this method, you must keep records of your actual cost.
  • The standard meal allowance, which is the federal meals and incidental expense (M&IE) per diem rate. The Foreign Per Diem rates website lists these rates by location. Note that lower rates apply for the first and last days of travel.
• The deduction for unreimbursed business meals is generally subject to a 50% limitation."

https://www.irs.gov/help-resources/tools-faqs/faqs-for-individuals/frequently-asked-tax-questions-an... 

https://www.irs.gov/taxtopics/tc511.html 

It's entered in the Meals & Entertainment area.   How to get to the area to enter your business expenses:  While inside the software and working on your return, type Schedule C in the Search at the top of the screen (you may see a magnifying glass there).  There will be a popup that says Jump to Schedule C.  Select that to get to the general area. 

Then:

• select Edit next to your business (if it is there)
• scroll to Business Expenses
• then Select Other Common Business Expenses
• on the next screen there will be categories and you can choose Meals and Entertainment

Where can I find this on the 2020 Home and Business Turbo Tax?

You can use the per diem rate for meals as a self employed person traveling to Taiwan and China.  There is no need to show a receipt for amounts up to $75 per day.

Here is a link to IRS Publication 463, with information about deducting meals.