Hi, I encounter this issue with ionic serve when I was trying to test mobile app after re-install ionic and node on newly installed catalina. Bye bye to Big Sur, Painful to try so far. Lets get back to point.
Error: Node Sass does not yet support your current environment: OS X 64-bit with Unsupported runtime
Reason for Issue: Node version was changed after re-install. To fix this issue we just need to build node-sass using npm command.
npm rebuild node-sass
After completion, Issue ionic serve command and error should be gone away.