I had a nomad in the late 90s/early 2000s. Lovely, chunky machine that I spent tons of hours with (pretty much always with a car adapter or AC adapter, cause Jesus, that power consumption).
I ended up giving it to my brother years later cause I just didn't see myself ever really playing again cause of the screen issues and everything else.
I also had an n-gage qd for a while, when they were getting clearanced out at Gamestop. It was cool, and at one point I had a complete set of games for it, although I ended up selling it all off cause I need to reduce my collection and at the time, it sounded like the hardware was gauranteed to fail with no real way to repair it, and I just didn't want to deal with that kind of stress.
Game.com I had for like, a month in the late 2000s, and it was just too hard to view the screen so I ended up getting rid of it.
My dad was a huge Atari and Sega guy in the 80s-mid 90s, so I was lucky enough to get to play with the Game Gear and the Lynx when they were current. I didn't really appreciate either of them at the time though (I was a pretty stupid kid, and remain a pretty stupid adult). As a grown up, I've come to really love each of them.
The Game Gear effectively being a Master System has resulted in me finding so many more Master System-esque games I never knew of, and while nothing in its library matches the greats of the Gameboy, I've definitely found lots of fun games for it in recent years. Also, I loved the TV tuner for it. I still remember the time my dad was messing around with it years later and hooked up my brother's OG xbox to it just to see if he could. Running Halo through a Sega Game Gear was pretty funny.
The Lynx is super fun too. A lot of its games were unique to the system and there was still so much new old stock stuff for it, with so little demand as of a few years ago, it was pretty easy to find games I'd never played as a kid. With the prices so low, I was happy to pick up a new game and give it a try 30 years later for that cheap nostalgia trip. My largest gripe with its games is that lots of them lack music, or only do music or sound effects at once. It also has way fewer games than its direct competition, and suffers the same issues as the Game Gear in terms of power consumption.