> Given that LLMs are just lossless compression machines, I do sometimes wonder how much better they are at compressing plain text compared to zstd or similar. Should be easy to calculate...

The current leader on the Hutter Prize (http://prize.hutter1.net/) are all LLM based.

It can (slowly!!) compress a 1GB dump of Wikipedia to 106Mb

By comparison GZip can compress it to 321Mb

See https://mattmahoney.net/dc/text.html for the current leaderboard