Ally Lotti's been posting content on OnlyFans for a while now -- but recently told her subscribers they could unlock the vid of her and the late "Lucid Dreams" rapper ... which she says warrants a XXX rating.

Now, as for an explanation for this move -- best believe this is drumming up outrage among JW's fan base -- AL claims to be under pressure by would-be bad actors. She writes ... "F***ed by my famous ex. Hackers are trying to threaten me to leak my old sex tape with my ex fiance Juice WRLD."

She adds, "IDGAF anymore. I’ll leak it myself. It’s a long time since I have been f***ed rough with some big black c**** like this. I am so mad that I am adding every nude I ever sent him. I know you will at least enjoy it. Can’t believe I am actually sending this but I can’t be threatened anymore."

While it remains to be seen if people are buying her rationale -- let's just say folks don't feel good about her throwing up Juice's private moments after his death ... it just feels gross.

Of course, Juice has been gone since 2019 ... and friends and fans weren't feeling Ally's excuse, hackers or not -- and demanded she have some dignity and take the post down.

One of the Juice WRLD's own collaborators, Denzel Curry, also weighed in ... and he thinks people (including Ally) should let him rest in peace.