This morning I quickly built an Android app that allows to handle Twitter and YouTube links to transform them into #Nitter and #Invidious links. Then it delegates the action to another app of your device.
It's open source.
The app is ready to be published on #Fdroid but I will proceed to more tests. You can use the debug apk.
 - Links in all other apps (mailbox, text message, from browser, etc.)