IETF QUIC broken?

This has been an issue for several months now, I am unable to use the IETF drafts of QUIC. However, the GQUIC / Google variant works perfectly fine.

In Google Chrome, however, the IETF drafts work perfectly. Is there any reason why it doesn’t work in Brave?

I’ve tried all 3 values for brave://flags/#enable-quic with the same effect.