https://github.com/stemrollerapp/stemroller
It can work with files you have on your machine, or you can use the in-built search bar to search YouTube for audio to use.
There are lots of websites that offer this service, but they usually restrict you to a certain number of files, or files of a certain length, with daily credit limits or mandatory sign-ups, and all that usual AI nonsense that annoys us daily. StemRoller is a program you install on your own machine (actually, you just extract it and run it from the folder), and so you can therefore use it however you like with no restrictions.
The results of any AI stem generation are usually pretty poor (for transcription purposes, at least), and it's no different with StemRoller. However, in certain circumstances, it really does help. For example, I'm currently tabbing a song where I know the drummer is playing a million ghost notes on the snare, but which I simply can't hear on the album recording. StemRoller's drum track output makes those ghost notes audible. The vocal output makes the backing vocals more obvious, too, which helps.
I wouldn't trust the guitar outputs for transcribing guitar solos or anything like that, but if you have a basic need like in my drum example, it could make life easier for you.
