I've been running Pd-extended on a Pi 3 and I've been having the hardest time getting the Fluid~ external working. I downloaded the external (https://puredata.info/Members/korayt/pdfiles/fluid.pd_darwin.zip/view?searchterm=fluid), extracted it and put the contents in a folder on my desktop. I then added the path 'desktop/externals' to my preferences, but when I tried loading fluid~ nothing happened. I also tried using the 'declare' object and that didn't work either. I also tried adding the files to the default externals location, however I kept getting permissions errors even after using 'chmod' and 'mkdir'
Any help would be greatly appreciated