It’s impossible to compete with Sony and MS. They put insane amounts of money in, and selling another $500 console to someone without the name/brand/library of the big two is hopeless.
Nintendo got off the GPU treadmill and started playing a different game. It’s the only reason they survived.
But other companies have tried doing a Switch like thing of taking an existing chip and making a console. nVidia and Google couldn’t do it and they have tons of money too. Steam had a niche, but a giant existing library (of a sort) and a strong name.
Sega has published the Yakuza series (supposed to be great), Sonic (let’s face it, garbage for 15+ years), and what? Their nostalgia is running low. They don’t have the money to make a Tegra 1 console.
And if they did? Who would buy it? Why risk buying that unless you’re a collector? I doubt they could undercut the Switch price much but the Switch has an amazing library and massive name behind it.
I don’t see how Sega could do any more than be a publisher/creator. Hardware is a losing game. The market is full.