There's this interesting handheld called "Begin" by MindKids, it's a Mega Drive real hardware clone (using a TCT chip, the good ones) with a built in EverDrive that allows it to run ROMs from a MicroSD card. Not shipping to UK or EU atm sadly https://www.aliexpress.com/item/1005006540839457.html
I'd considered contacting them to see if there was a way I could buy one but I doubt I'd use it regularly & I'm not really feeling "buying things just to have them" at the moment. But I thought I'd share it around anyway because I'd like to support this kind of interesting development in the field
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The pictures in the listing also show a NES version which doesn't seem to be available at the moment
As the name implies this is the first handheld from MindKids, theyre mostly known for aftermarket cartridges but have made a handful of clone consoles, notably the ShellNES which was built into a cartridge shell. The development & engineering is done by the owner, it's basically a one man operation