I’d recommend a desktop machine, or an NAS. I am unaware of any ‘free’ services that allow you to upload and store data. 

The cost (and legal risk) of storing peoples music killed off the free services for this years ago.

iBroadcast works really well for me, and it is among the services available to link in the Sonos app.

Hi @Wendyzx6 

Welcome to the Sonos Community!

YouTube Music currently allows the uploading of up to 100,000 tracks for non-paying customers.

Hi Corry, thanks for your reply. I think you need to have a premium account to play YT Music through Sonos unfortunately. 

I'll give it a go anyway. Do you know where I can find instructions on how to upload my mp3 files to the free version of YT music. Its not obvious to me how to do it

Hi @Wendyzx6 

The information I have is that you can do so with a free account.

Open the YouTube Music page on your browser, make sure you are logged in, and literally all you need to do is drag-and-drop your music folder on to the website and the upload starts.

I hope this helps.

@Wendyzx6

Just tested it on mine works fine for me and I don't pay

Uploaded my collection years ago and it plays on sonos ok

Just cannot add stuff to my sonos page

Also if you have an amazon prime account there is a free music streaming service you can use

Yeah, that helps lots. Thanks Corry

Thanks @skullc , I really appreciate the reply.