Just a quick heads up. I missed some DMs on Reddit because I have a FF extension to automatically redirect me to old.reddit.com because the notification indicator at the top wasn't lit.
I discovered the same thing, but when I saw the DMs I missed over the years I was glad to have missed them. They were all scammy.
I have been doing this using iOS Shortcuts and a regex for years. Except instead of old I redirect to a redlib instance.
StopTheMadness free iOS browser extension can redirect arbitrary URLs based on regex.
StopTheMadness didn’t fit my needs iirc. I have heard “Redirect Web for Safari” is a decent alternative solution though, have yet to try it
At least it has worked reliably for old.reddit and yt->invidious.