If you redistribute GPLed binaries you have to be willing to provide the source that built that binary, whether it incorporated changes or not, to anyone who asks. “Provide” can include pointing someone at a public repo these days.
https://www.gnu.org/licenses/gpl-3.0.html#license-text, article 6a:
“a) Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by the Corresponding Source fixed on a durable physical medium customarily used for software interchange.”
Assuming any “durable physical medium customarily used for software interchange” still exists, that means that, if you choose to ship your software on CD you have to give the source to whomever you distribute the binary, but need not make the source code available to others.
If, instead, you go for the distribution method of article 6b, you do have to make the source code available to anyone who possesses the object code, but not indefinitely:
“b) Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by a written offer, valid for at least three years and valid for as long as you offer spare parts or customer support for that product model, to give anyone who possesses the object code either (1) a copy of the Corresponding Source for all the software in the product that is covered by this License, on a durable physical medium customarily used for software interchange, for a price no more than your reasonable cost of physically performing this conveying of source, or (2) access to copy the Corresponding Source from a network server at no charge.”
So, if you distribute the binary in a “physical distribution medium”, and then immediately claim to stop supporting that product, I think you’re off the hook if nobody asks for the source code for 3 years.
Also, should that “(including a physical distribution medium)” have been there in that article in the license? It means you can sell a CD with your software, immediately stop supporting that CD, and get of the hook in 3years time.
These days you can just post a link to a github repo on your web site
Which they can resolve by asking you for it, so not much of a loophole.