I use https://freetubeapp.io/

On mobile, Firefox plus ublock works well. There are a few issues like losing your position if the page reloads, but it works pretty consistently otherwise.

I also use NewPipe, but Google breaks it fairly regularly.

Actually, I have never used piped and invidious to watch the videos themselves. I use them just as subscription feeds and in case I need to search for some video, then I toggle a script I have, I copy the links to the videos I want to watch and I untoggle the script. Then the links I copied start playing on mpv. I don't like to overload piped and invidious services, which I would say is the main reason for them to be shut down, when I can watch/download the video through mpv-ytdlp on my own. Although, I don't know if that answers your question.

FreeTube is a useful project as it allows you to "fallback" on a non-preferred frontend.

https://github.com/FreeTubeApp/FreeTube

This allows you to continue to use Youtube irregardless of which frontend is (potentially not) working.

In 'Settings > General' you'll want to select "Invidious API" as your "Preferred API backend" and specify your favorite invidious instance in the "Current Invidious Instance" field and click "Set Current Instance as Default". This locks FreeTube into the specified instance.

Then, when you notice that FreeTube is issuing notices to you about your favorite Invidious Instance being down, you can wander back to 'Settings > General'; hit the "Clear Default Invidious Instance" Button and wait as FreeTube magically contacts the "https://api.invidious.io/" page for you and selects a new, and hopefully online and working Invidious instance. (You may have to hit this button several times to roll a working instance, Hit the button, check the subs page and see if everything loads, repeat if it falls back on the Local API.)

When you run into instances where you can't roll up a good Invidious instance; the built in Local API is running a NewPipe Extractor like API directly from your FreeTube client. Not the best; but at least it keeps things working while you wait for the Invidious devs to fix things up; and it still reasonably preserves as much of your privacy as it can while doing this to the best effort it can.

...Sadly this doesn't work when Google manages a double combo of breaking both Invidious and NewPipe; but I have found that this is less often the case and the devs of either project are usually fairly quick about getting fixes out. Bless their hard work with a donation sometime maybe, if you can.

I use grayjay as you can use a google account to bypass the "confirm your not a bot" but then have the ability to subscribe, comment, and save video playback without a google account.

I wish we had some sort of way to copy videos from YT to PeerTube on some sort of on-demand way.

Like tell PeerTube the video you want, wait a few minutes, and then its available for everyone. Then it auto deletes after X days if it has had 0 views.

Edit: oh man, you could even have a Lemmy bot do this automatically when it sees a link to a YouTube video.

I signed up for PeerTube, uploaded all my videos there, and updated my old YT vid descriptions that say "can't watch this video? Click here to view ad-free on PeerTube"

New pipe android app. Been using it for years with no issues accessing YouTube.

I feel like most have misunderstood the point of the question, they offer to use newpipe, yt-dlp and the like, but those aren't private, they just allow you to watch without signing in, just as you could through the official website with maybe uBlock origin, you're still exposing your IP.
The only fitting suggestion I saw is that of downloading from invidious through yt-dlp, which sounds pretty neat, I had no idea you could when the web frontend is apparently not working