My understanding is that the caret is the answer for traditional SemVer, i.e., there will be breaking changes prior to 0.1.0, there may be breaking changes between minor versions prior to 1.0.0, and there may only be breaking changes between major versions above 1.0.0.

The TypeScript team has made it clear. They do not follow semver. "minor" (X.X) releases can contain breaking changes. Major releases (X) have very little meaning.

For better or worse, TS doesn't do semantic versioning; see #31761

Unless we choose to use the semver ju-jitsu of calling the changes a bugfix

The versions must be compatible, so if a peerDependency is listed as 2.x, you can’t install 1.x or another version. It all follows semantic versioning.