Composer says it cannot resolve dependencies during the upgrade. Can you fix it?

Yes, this is one of the most common upgrade blockers. The message Your requirements could not be resolved to an installable set of packages usually means a third-party module pins an old constraint, an abandoned package has no build for the new Magento metapackage, or a PHP version constraint clashes. We read the dependency tree, find the package that is actually blocking the resolve, and fix it by pinning a compatible version, swapping to a maintained fork, or patching the constraint. You get the corrected composer.json as a reviewable diff.