I think the SteamDeck might be overkill here. Something along the Miyo or Anbernic is what I'm thinking initially, but I have no idea what in this product category is worthwhile.

I had a Steam Deck and gave it to my partner because it's gigantic and unwieldy. Just a heads up for the small-handed individuals. The thumb-sticks felt like absolute garbage as well. Hilariously, the biggest thing I can say - is that while the device itself was gigantic - the screen felt relatively small. I decided in the end, to get an old Chromebook and convert it to a Linux based system for all my gaming needs. It's thin, durable, and has an extremely long battery life. I can see the screen inside and outside. It actually feels lighter than the Deck because the weight is evenly distributed through-out it's form. I am very happy with it.

I considered the Miyoo Mini+ but figured I would run into a similar issue where I realized that I was no longer a child and that a Gameboy perhaps isn't the best form factor for an aging gamer. But I think it's quite portable and it might make a solid system.

Steam Deck or the miyoo mini plus with onion os would be my picks. I have both and they both scratch an itch in a different way.