Getting audio files from insta/youtube/spotify (UK only)

Hi all, I want to make some photo compilation videos for a few different people. I've done this successfully on Canva and Capcut before, but using either generic music or audio files I already had. I want to use specific music (one instance being You, Me and Steve, for example) but am having trouble finding audio files from existing videos. Back in the day I could just bung the youtube link into an MP4 to MP3 converter and it did it pretty much immediately, but these days I'm finding either that these don't work in the UK because of our online safety/copywrite laws, or they look so scammy and want me to download something. I don't want malware on my computer.

How do I get audio from an insta reel or a youtube video and turn it into an mp3 file for my videos? Google's advice keeps turning me back to one of the sites I'm suspicious of, so I'd rather have direct recommendations from people who actually use these tools.