Hey @paulmccarthy sorry for this late answer. Thank you for your answer.
I tried installing fsl with the command you gave me, and then with miniconda installed directly on my computer, also tried using conda, and using advices given in : Problems installing FSL - #30 by Tru_Gamble such as doing the installation in a created conda environment.
I always end up with the same problem : the 3rd step of installation stuck at 0% and an error message with the log file mentioning "/Users/asavalle/Dev/fsl/bin/conda env update -p /Users/asavalle/Dev/fsl -f fsl-6.0.7.16_macos-M1.yml . ". I have no trace of this yml file, maybe there is something i could do there ? Thank you in advance for your help