Hello,
The obfs4 executable shipped currently misses a fix (commit
`393aca86cc3b1a5263018c10f87ece09ac3fd5ed`) that should in theory make
the traffic truly indistinguishable.
This is the Tor Browser ticket:
https://gitlab.torproject.org/tpo/applications/tor-browser/-/issues/40791
And this is the repo:
https://gitweb.torproject.org/pluggable-transports/obfs4.git/
The shipped executable should be on git main or tag 0.0.12.
Would be great to fix this in Debian:
https://tracker.debian.org/pkg/obfs4proxy