Mother 3 got a surprise announcement for the Switch Online service yesterday, but the catch is it's only available in Japan.
To add to the pain, Nintendo has now released new Switch Online icons based on the Famicom title EarthBound Beginnings. They will be available until 28th February 2024, so be sure to redeem them with your Platinum Points while you can.
EarthBound Beginnings was originally made available for the Switch Online service in February 2022. As for the third game, it's out today on the Switch GBA app. You can download this particular version of the app with a Japanese Switch Online account.