Are app stores that host free yet copyrighted APKs without the author's explicit permission legal? Examples include APKMirror and APKPure.
It is legal to have a website that distributes software, for money or for free. However, such a website might bear some liability for copyright infringement, if a user uploads protected material without the permission of the copyright owner. This was the case with Grokster, which was found to have induced copyright infringement, and subsequently had to pay $50 million.
There is a provision in US copyright law, the Online Copyright Infringement Liability Limitation Act, which sets forth conditions whereby a website can protect themselves from such liability. There are particular steps that have to be taken to officially complain and correctly respond to a complaint. If a pirate uploads someone's software without permission and the software owner learns about it, the owner can follow the takedown notice rules and the website operator should remove the offending material. If they do not remove it, they may be found liable for contributory infringement. The pirate could file a counter-notice (which could result in a perjury conviction, since the pirate knows they do not have permission). Once the notice and counter-notice have been filed and the parties notified, the other has 10 days to sue (you put the material back up if no lawsuit files within that period).
The Online Copyright Infringement Liability Limitation Act is Title II of the Digital Millennium Copyright Act (DMCA) , and is probably beter known under that name.