Hi @Mayu how did you first deploy your web apps?
-For your Linux web app, check the WEBSITE_NODE_DEFAULT_VERSION app setting is set to 18LTS or another higher version. This overrides the default node version.
-You can also try using this cmdlet that was shared in the post you referenced to set the node version to 18LTS
az webapp config set -g YourRGName -n YourAppName --linux-fx-version "NODE|18LTS"
Please let us know if you have further questions.
Best,
Grace