yeah i noticed after looking at the list that the games using those missing mappers were licensed.
is it a case that all of them can not be supported on the carts we already have available? maybe some of them krikzz has not added support for yet. when it comes to extra hardware then that is a different matter.
all those unsupported mappers use extra hardware?
Almost all unsupported mappers has some kind of special hardware in the cartridge. MMM01 and unlicensed mappers like Sachen, Wisdom Tree and Rocket Games are the main exceptions, so maybe the Everdrives could add support to all of them in OS updates.
Here are the main unsupported cartridge types:
MBC6
Has some flash memory on cartridge. Only "Net de Get: Minigame @ 100" uses it. You could download mini games using the network adapter and store on the flash.
MBC7
Accelerometer for tilt-sensing (not gyro-sensor as I said above). Used in a Kirby game and Command Master.
MBC30
A variation of MBC3 only used for Japanese Pokemon Crystal. Allows up to 64kB SRAM instead of 32kB, otherwise identical to MBC3 I think. I'm not sure if any Everdrive supports this or not yet.
HUC1
Hudson's MBC and has the "GBKiss", an IR-communication device like on the Gameboy Color. Although used mainly by Hudson games, Nintendo also used it for Pokemon Card GB.
HuC3
Has GBKiss, RTC (probably not accessed the exact same way as the MBC3 RTC) and a beeper used as a kind of alarm when the game is sleeping, like an early form of streetpass.
TAMA5
Also has RTC and a beeper. Used in Game de Hakken!! Tamagotchi: Osutchi to Mesutchi.
MMM01
A licensed multicart mapper used by Taito Variety Pack, Momotaro Collection 2 and a Chinese variant of the Taito Variety Pack, "Mani 4 in 1".
Game Boy Camera
Obviously has a digital camera in the cartridge.
Then there's the MBC5 rumble feature which isn't supported by any Everdrive.
Here is a nice list:
https://gbhwdb.gekkio.fi/cartridges/