No. According to an article the IDs were from people who were challenging an age determination. Still bullshit, but you don't need ID to use Discord as a general rule.

The unauthorized party also accessed a “small number” of images of government IDs from “users who had appealed an age determination.”

Small is, of course, a relative term. I would consider a small number to be 2 or 3. They may feel that 10,000 users is a small number. Who can say?

Apparently if they get flagged as underage when they aren't.

Yet another example of how requiring ID is a shit idea.

When I use the linux or web client it asks for a selfie with my ID card when I try to enter a server.

Works fine on Android.

Contacted support, they say my account is not flagged as underage but I have to submit the photo anyway. I told them i won't.

In the United Kingdom yes because of our authoritarian Online Safety Act that came into power earlier this year. If I join a discord channel marked as nsfw I get a prompt for id which I bypass with a VPN in another country.

Normally, no.
And this data breach wasn't technically to Discord either, it was to a third party company that does some part of customer support for them and the data and IDs leaked were from people who had contacted support because they were flagged underaged, and sent their ID to verify they weren't.

Which also kinda explains why they weren't deleted as they should be, they were just attatchements to support tickets, and not a "proper" verification system.