For UDP you’d also usually reencode packets as http3 warp ones [...]

Is this similar to when you mask it as webrtc?

Sorry I probably meant QUIC not warp. It is related, I think webrtc now usually uses quic, so masking as quic or webrtc are probably synonymous, but honestly I don't know enough about the details to say for sure.

Something other than DAITA?

I know people in Russia are reporting Mullvad gets fully blocked, so I don't think DAITA is enough. As @chimp@lemmy.dbzer0.com mentioned, Hysteria is more in the right direction, though in more modern iterations/forks and together with another layer of obfuscation.
I don't generally like to shout out names too much, since popularity among those that don't need the tools makes them more cracked down upon for people that do need them. So I'll just say that for the less obfuscated but more responsive route via rtc you use an updated hysteria as the outer layer, containing a fully homogeneous encrypted stream from a tool named after a reptile.

As per the GDPR or something else?

Mainly Net neutrality rules. Net neutrality just barely allows basic DPI, though it already heavily restricts what ISPs can actually do with that inspection. Wikipedia: EU net neutrality violations. Note that the 2007 case there happened well before regulations were strictened.