TrimUI Brick arrived!
My first impressions are overall really positive, though there are still a few quirks to work out.
The size, controls, and overall feel are great. I had been a bit worried that it would be too small or feel uncomfortable, but it's a good size. It's very solid feeling. The D-pad and buttons remind me of my old DSi, which I always liked. Everything is kind of clicky in a satisfying way. It feels great to hold and I did not have any issues even after playing for a while. The screen is plenty big, and it has the same DPI as my iPhone. I set everything to aspect/full height or width and "crisp" and I have not noticed any thing that looks off. Even GBA games look/feel good, despite being a bit wider than other systems.
MinUI is great... on the systems I have working. Game Boy, GBA, NES, SNES, Master System, Genesis, NGPC, and TG16 are all perfect. I had to search around a bit for bios, but all of the roms I loaded work and it's easy to navigate. The unified menu is really nice, and I set up the function keys to save and load, which I've already used a lot. Whenever you turn the system off, it automatically creates a save state and then loads it when you turn it back on. There's not that much to it, you just pick a game and play. It's very much an OS that gets out of your way. I only played around a bit with ordering games/systems and creating collections, but it seems like it will let you customize a ton.
Pico-8 works well too. You can apparently trick MinUI into using Wifi and use the Splore tool to download games directly, but I just saved a bunch of cartridge images on my SD card instead. One negative - the menu button doesn't work while playing Pico-8, and you just have to use the pause menu to close the game. I think you have to manually quit games to turn the system off too. It's not really a problem, but it would be really nice if that just worked as well. Maybe it'll get added in later.
Problem systems: Dreamcast actually worked fine for me, but not perfectly. Also, the back of the system did start to get hot after playing for like 30 minutes and the screen is a bit small for these types of games. It's cool that it's capable of this, but I will likely not play DC games on it again. For whatever reason, I cannot get Playstation or TGCD games to start. I have never been great with CD based Roms. The ones I have use bin/cue files, and I suspect I may need to convert them to ISOs? Or maybe I have the wrong Bios? I honestly don't know. And from what I've read, DS and Portmaster games are tough to set up. I may leave those for a later project. Oh, and Arcade games are a mess too. I know that I want Final Burn Neo roms, but I have no idea what bios I need. I might just download a full set that includes bios. I don't really want a ton of games outside of the core systems that work well above, but it would be really nice to have a few 2D games from other systems like Cave Story, various Castlevania games, etc. But then again i have these on 3DS/Vita and ultimately if I don't add them here it won't be the end of the world.
One last issue - the LEDs are wonky. The shoulder button ones are white, the function buttons are green, and the top led does not turn on. I read that you can fix them by changing themes in the stock OS. I can take out my SD card to load stock OS, but it only has one theme and I think I need to install stock OS (or stockmix/crossmix?) on a separate SD card to add more themes. I would honestly be happy if the LEDs were all deactivated, but MinUI just lights them up for a second when you turn it on or off, and if I can get them to all be white that will be good enough.
So yeah, if you just want to play 16-bit games and pico-8, it's a perfect little machine for that. Adding other systems and features seems a bit messier. MinUI is great when you have it set up, but there is a bit of work involved in getting to that point. I will keep tinkering and check back in when I make some more progress.