The new system is here: https://edits.nationalmap.gov/apps/gaz-domestic/public/search/names
But all is not lost, because they have made the
previous GNIS database available by states as
comma-delimited text files, available here:
I downloaded the Tennessee file and have created a
spreadsheet for it in LibreOffice. The very large
spreadsheet (6 MB), sorted first by county, then by
feature name is here:
TN_Features_20210825_sorted.ods
I have also created individual file for each county
from this spreadsheet, available from the following links.
My old Excel 2011 (Version 14.6.1) will not open or import
.ods files, but later versions will do so. I expect
any version of Excel should be able to open the original
text-delimited file, which I did in LibreOffice to create
these files, although it did take a bit of work to get
them to the current forms.
If you would like to try LibreOffice, it is free, although
donations are appreciated, and is available in both
Windows and Mac versions:
https://www.libreoffice.org/download/download/