For some reason, every time I launch renoise (3.5.1) it restarts the scanning process of ladspa(s) plugins. I tried to remove all the caches from ~/.config/Renoise/V3.5.1/Cache* but it did not solve the problem.
After renaming the Config.xml it loads instantly!
tbh, I am not using so many LADSPA. I just re-enabled in the settings LADSPA scanning out of curiosity and I will let you know once it finishes scanning.