which are other low-cost intersting hardware/electronics/chip/projects (some i like are rtl-sdr, fpga, rpi, ardiono, esp-32) ?

@frend Rock Pi 4B or Asus Tinker board are pretty cool.

@matrix thanks for suggetions. those stuffs are ppart of boards, i am listing them. do you have more suggetions except boards?

@frend Well, this isn't low-cost, but it's relatively cheap for it's category.
https://www.indiegogo.com/projects/gpd-micropc-6-inch-handheld-industry-laptop#/

@matrix do you know this year CES has launched many portable display, so it would be very bright future to have portable powerful/gaming PC in future

@frend No, I'm only aware of the foldable displays companies showed there.

@matrix are you from japan

@frend Nope. I'm from Europe.