Please note that yt to mp3 is for downloading legally and only in the structures of copyrights and other terms led down by YouTube. You can download it directly or use third-party software to grab youtube videos but remember that downloading content from YouTube without their permission other than offline button (YouTube Premium), is forbidden. YouTube only allows video download legally with the creator's consent, or if YouTube itself has provided a feature to do so. A Reining Industry Association of America (RIAA) 2021 report stated that illegal stream-ripping account for about more than 90% in terms of music piracy and this puts a lot out there concerning where the line on legality becomes fuzzy.
You can consider using the services by YouTube to do so, for instance with another plan like Youtube premium you will not face any legality challenge on downloading yt and then later converting it to mp3 as well. YouTube Premium — allows users to download videos straight through the app and saving them for offline usage however you cannot only extract audio as a separate MP3 file. But this option, still legal, is going to be your better means than getting onto these options and not following YouTube guidelines. With YouTube Premium, which costs $11.99 a month, you also get ad-free viewing and offiline downloads as well as background play.
Or you can also use copyright free content on YouTube. Many creators apply Creative Commons licenses, which enable users to download and redistribute content legally. You can search for these videos licensed under CCL on YouTube and you can convert them to MP3 with trusted tools There are the 1.6 billion Creative Commons works worldwide, that can be reused legally as well (and they have a wide range of content).
Conversely many artists and content creators offer direct access to the downloads of their work, whether via official third-party stores like Bandcamp or through unofficial channels on freebie blogs. For example, on Bandcamp you can purchase music directly from the artist and everything is legal. Not only that, but it is legal for users since they are not copying anything unauthorized and this will support the creators again.
Alternatively, you can ask directly to the content creator if he/she allows downloading. A few creators might permit you to use their videos or audio as long as it is for personal, educational or non-commercial purposes. Despite its manual nature, this way seems to be the most legal and considerate towards copyright holders.
In the words of legal expert Lawrence Lessig: "Law makes creativity easy, but also only easier. This statement emphasize the critical balance of following legal frameworks and enabling creative ways to interact with content such as yt mp3 conversion.
If you are interested in finding responsible tools & resources for conversion why not visit yt to mp3 and search legal compliant sources.