Breaking
The only breaking change in v18 is with the -g/--global flag.
npm-check-updates -g will now auto-detect your package manager based on the execution path. Previously, it defaulted to npm.
yarn dlx ncu -g --packageManager yarn→yarn dlx ncu -gpnpm dlx ncu --global --packageManager pnpm→pnpm dlx ncu -gbunx ncu -g--packageManager pnpm→bunx ncu -g
If for some reason you were running ncu -g with an alternative package manager and relying on it checking the global npm packages, you will need to now explicitly specify npm:
ncu -g→ncu -g--packageManager npm
Thanks to @LuisFerLCC for the improvement (#1514).