A recent PG forum thread is discussing it. PG deemed it not secure enough almost three years ago, based on solid reasoning.
However, that was three years ago and the product has altered dramatically. I just don’t think it’s been resuggested/evaluated since then.
PG forum users (and PG itself) are pretty inconsistent with how they judge stuff. Not trusting one company (Filen) because there were issues three years ago (and are now, as I understand it, fully addressed) but totally trusting another company (Brave browser) despite repeated actions that erode trust is odd behaviour.
I’m a filen user myself, just in the interests of full disclosure.