the problem with the term "sideloading" is that it's a propaganda term, intended to suggest some impropriety in your wishing to choose the instructions that your computer should follow, to shame people into suppressing that wish. it's nothing to do with how common it is, or whether the program you wish to install comes from the internet, from a friend, or you write it yourself. they're all "discouraged" by that who purports to own your device, control the software that runs on it, and, through that software, control you