

I assumed it meant using a separate device or software on the side
That’s what it is. I remember actually sideloading apps to my BlackBerry 10 devices (Z10 and Z30) (though it really wasn’t that long ago not to remember it…) using a PC with a Chrome based browser (though it worked on Firefox too with some minor fiddling) to push and install .bar files to the phone. That is what sideloading to me.
Now this term changed, so everything you install from a different source than the built-in appstore is called sideloading, which is ridiculous IMO.





I remember when carriers not just locked the phones, they also had custom firmwares filled with bloat and customized skins and even locking down features and all that shit. For example, I had a Sony Ericsson K700i and it had a disgustingly customized FW on it, and aside that it was ugly, I could only play MP3 files that I purchased through Vodafone. Sending them via bluetooth (or even with IR) didn’t work, the phone refused to play it back.
(Then of course I found out that Sony Ericssons were pretty moddable phones so I replaced the FW with an original one and that solved all my problems. For some reasons, the fact that I patched the FW with countless of VKP patches and even unlocking it with a patch, didn’t void my warranty so whenever I fucked up the FW beyond my abilities to repair it or simply bricked it, I just sent it to Vodafone and they fixed it.)
And they did this even when Android became a thing. (Though, it was a Vodafone branded phone so… it was sort of OK. (technically it was a Huawei though, also pretty moddable phone))