Two related, automatic improvements for how a published Web Application shows up to search engines and to visitors using a screen reader.
Per page language
Each page already has its own Language field in its page settings (the same field the Language Switcher block, see "Comments, Multi-Step Forms, and other advanced blocks," links between). Whatever you set there now also correctly marks that exact page's language for a screen reader and for a search engine reading the page, so a French page you've built is correctly announced and indexed as French, not silently left as English. Setting this remains entirely manual, per page, there's still no automatic translation, building each language's own page is still on you.
Sitemap and robots.txt
Every published app automatically gets a sitemap (listing every real page, so search engines can find them all) and a robots.txt (pointing at that sitemap), the same way a published Website project already does, at /app/yourslug/sitemap.xml and /app/yourslug/robots.txt or at the matching path on your own connected domain. A page with its Admin only setting on is left out of the sitemap, since that's your own back office page, never meant to be found by a search engine. While maintenance mode is on, the sitemap is served empty and robots.txt asks crawlers not to index anything, since every page is temporarily showing the same "we will be back soon" placeholder instead of its real content, this reverts back to normal the moment you turn maintenance mode off.