There's a seemingly redundant pair of grid-container/grid-row divs wrapping blocks added to the secondary footer region in the block layout. In page.html.twig, looks like there's a pair of these divs just inside the usa-footer__secondary-section div, and then another pair inside the if page.footer_secondary code.
The end result for my site is that my custom content added to the secondary footer is restricted in width, even when I use CSS to set max-width: none for grid-containers in the region (not entirely sure why this doesn't work).
Install USWDS and add a block to the Secondary Footer region in Block Layout.
Remove the grid-container/grid-row divs inside the if page.footer_secondary code in the template. This works for me, but I'm also not using the "built-in" content for the secondary footer. Maybe a more general solution would be to use one grid-container with two grid-rows, one for the built-in content and one for the custom content?
Closed: works as designed
3.7
Code
For your customization on your site, were you able to change the twig in your subtheme to fit your needs?
Closing due to more than one month with no response.
Oops, sorry, apparently I wasn't subscribed to email notifications. Yes, I've customized the twig to work as desired. Thanks.