The 10+ minutes that OP observed where in tortoise (=9) mode tho. That's the slowest mode, comparable to "placebo" mode in x264, and meant as a "test" mode, not

The 10+ minutes that OP observed where in tortoise (=9) mode tho. That's the slowest mode, comparable to "placebo" mode in x264, and meant as a "test" mode, not as a daily driver. The libjxl default is "squirrel" (=7), and you can go as low as lightning (=1), so you have a choice to trade compression efficiency for compression speed. Additionally, there are different decoder modes (in the encoder), allowing you to make tradeoffs between efficiency/density vs speed. But yeah, libjxl will remain slower than libjpeg-turbo, especially on encodes.