What's the best privacy friendly way to use discord on android ?

You can try all you like, but the reality is that as long as you're logged into their service (which you'd need to be to use it), they will track you in ways that you can't shield yourself from.

If you want to try:

• Set up an account and use the service through a VPN.
• Register using email/names/information that is not linked to your actual personal info.
• Use a DNS adblocker, or something like Adguard on Android to block any app-side trackers.
• Opt out of whatever you can through Discord (not that I think they abide by it, but all you can do is try).