Maybe invidious or use freetube.

There is also grayjay, and while it works pretty fine I believe there where some controversies around the program even tho I don't know the reason.

freetube recommends decently similar videos with the occasional slop in there, in addition to your subscriptions that are not visible to google or anyone else. only here, when you hide a channel, that thing is hidden forever, won't pop up again randomly.

I know that's not exactly what you're looking for, but imo not getting recommendations from YouTube's algorithm at all might be better. Why? From the Cambridge analytica scandal we have proof that these algorithms have the capability to manipulate people's ideologies without their consent. I think your algorithm basically personalizes an indoctrination strategy. The idea is not new, it has been talked about in the famous book 'Manufacturing consent'.

Let's say, they don't have a grand political plan behind their algorithm, but even then, the algorithm is just optimizing your feed for maximum engagement rather than intellectual nourishment. They just want you to watch more and more. And not spend much time to stop, think and reflect.

As for recommendations, you can get them organically from your close friends (they'd def be happy to send you a bunch lol) or from lemmy communities (like the documentaries ones)

smarttube fdroid has been working great for me

Why is no one mentioning Flow? It is literally built to be exactly what you want. It has a local, no-Google-account required recommendation engine.

What types of videos do you watch?

Unfortunately, there's nothing close to the actual algorithm. You either use YT without an account in a privacy-focused web browser with uBO installed. That's as far as you go. And of course, sensitive and political topics are always to be watched in NewPipe/PipePipe/LibreTube etc.

I use a front end called Grayjay. You can log in with your YouTube account in the settings and transfer everything over, or you can set up a Polycentric account and never use YouTube directly at all. It's ad-free on my device and I notice that it even shows locked Patreon content on some channels.

I downloaded it directly from their website and use F-Droid as the repository. I was able to do all this on an Android tablet, so it's fairly simple.