Comment and/or doc changes. / Minor test/demo code fixes. / Minor dead-code removal from build script(s). / Pulls in: [flow] CI pipeline: Tweak to get gcc-13 builds to work again (GitHub changed preinstalled packages).

Comment and/or doc changes. / Minor test/demo code fixes. / Minor dead-code removal from build script(s). / Pulls in: [flow] CI pipeline: Tweak to get gcc-13 builds to work again (GitHub changed preinstalled packages). #837