Insert HTML Tables - new Google Sites
Add tables to an new Google Site by embedding your own HTML table
Embed HTML Table - new Google Sites
Write your own HTML and CSS for the table and copy
On your new Google Site use the Embed option on the right-hand INSERT panel
Use NEXT to preview your code and if happy use INSERT to add your code
Resize and move as appropriate.
Tables are difficult to make mobile responsive and the embed code tool doesn't offer a dynamic height. If your table needs to get longer on a tablet or mobile you'll have scroll bars on the embedded code.
Content in the EMBED CODE tool does not get indexed by the site search or Google Search