Just to point out, that even though these things are not listed in the Discoveries section of the Codex, if you scan the logs at these places, they are listed in the Commander section of the Codex, under "Archive". You can re-read all of the logs of any generation ships, INRA bases, Tourist beacons etc that you have scanned.
As for "Are they detectable with the FSS", some are, some are not. The Generation ships in orbit around a planet are detectable if you probe the planet; the ones in deep space ("orbiting a star rather than a planet") are now completely invisible. This has been bug-reported.
On the plus side, tourist beacons are now made visible as a distinctive-frequency USS on the honk, which can be scanned even at infinite range. And the Voyager probes in Sol system are likewise revealed on honk and scanning their USSs, so you no longer require a convoluted navigational procedure to find Voyager 2, or the tourist beacon in VY Canis Majoris. I found the Voyager 1 probe, and and tourist beacon right next to it, from the honk of Sol and sailed straight out to them.
As for "Are they detectable with the FSS", some are, some are not. The Generation ships in orbit around a planet are detectable if you probe the planet; the ones in deep space ("orbiting a star rather than a planet") are now completely invisible. This has been bug-reported.
On the plus side, tourist beacons are now made visible as a distinctive-frequency USS on the honk, which can be scanned even at infinite range. And the Voyager probes in Sol system are likewise revealed on honk and scanning their USSs, so you no longer require a convoluted navigational procedure to find Voyager 2, or the tourist beacon in VY Canis Majoris. I found the Voyager 1 probe, and and tourist beacon right next to it, from the honk of Sol and sailed straight out to them.