It all stems from a datamine dating back to 2019 - which revealed four emulators inside Nintendo's NES app. While the purpose of the remaining emulators still hasn't been revealed, both Nate and his co-host 'MVG' believe the third one 'Hiyoko' is likely for "Game Boy and Game Boy Color" titles.
Nintendo Life has also confirmed with its own sources that Game Boy and Game Boy Color titles are likely coming to the Switch Online service "really soon".
Source
Searched GameBoy and Game Boy and it didn't come up, but close if old.
Could September be the month Mole Mania finds its way to the Switch?