A backdoor in xz

> And LZMA does not add match (anything?) over ZSTD.

I don't remember all the details, but ~ 8 months or so ago I experimented with replacing xz with zstd for fs images at $dayjob - and while zstd was a LOT faster, even at max zstd level the files were still ~ 20% larger than a plain xz -7. (xz -9 was too slow to be practical) Take the exact number with a grain of salt because it's from memory, but the difference was significant.

In our case the significantly higher compression ratio was worth it.

Can't speak about systemd, but I would definitely not make any absolute statements that there are NO advantages to xz/lzma.