Upgrading from 1.x

2.0 validates strictly and fails the build instead of rendering invalid data. Most upgrades come down to fixing what the build reports.

Run a build. Every invalid prop is reported with component, page and field (see Validation). Unknown props and unknown integration options are errors now, too.
Provide values that used to be invented: LocalBusinessSchema and OrganizationSchema need a name, JobPostingSchema a hiringOrganizationName (each can also come from the configured defaults). baseSalary needs a unit. employmentType, operatingSystem and applicationCategory are no longer defaulted: set them explicitly where you relied on 'FULL_TIME', 'Web' or 'DeveloperApplication'.
Graph mode: keep exactly one <SchemaGraph /> in the base layout. Its position no longer affects which schemas are included.
Online events: use attendanceMode="Online" with onlineUrl instead of a placeholder address.
Options: defaultArticlePublisher is { name, logo?: { url } } and defaultLocalBusiness takes the LocalBusinessSchema props.
Meta tags now come from the middleware and are inserted into <head>; tags your layout already defines are kept. A workaround for meta tags ending up in <body> can go.

The full list of changes is in the changelog.