best way to share to tablet and phone users?

goshawk on horseback

hello all,
does anyone have any ideas on the best way to share audio files to tablet and/or smart-phone users?
the reason for asking this, is that I have recently joined a new whatsapp group about audio books, and have mentioned about some of the one's I have remastered from tape over the lockdowns. I have now had a number of requests to share them, but being a whatsapp group, the majority of it's users are on tablets or smart-phones only, so the usual .zip files on sendspace, dropbox, or what ever, are probably not going to work for them, but so far, it is the only method I have used, so I don't know of any others.

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