Disclaimer: I am not a tax professional.
TLDR: The easiest way I found to find adjusted cost basis with sales that have 0 in the cost basis, like RSU or ESPP, is to use supplemental information supplied by the stock broker.
See if your bank or broker (or administrator) provides a supplemental document for your stock plan. This will have more details about each transaction such as "adjusted cost basis"
I entered each sale manually and indicated that the sale was for RSU/Stock Plan using the prompts.
With this doc it was very easy to select "I need to adjust my cost basis" and then refer to the supplemental doc for each sale to enter the adjusted cost basis.
Probably a good idea to verify the numbers in the supplemental info with the calculations mentioned in above posts, but if you trust your broker's Information systems , and the supplemental info, using the form saved me a lot of time and headache.
