https://github.com/znoxx/torbox

https://wiki.debian.org/FreedomBox/Manual#FreedomBox.2FHardware.Supported_Hardware
89 USD, RAM 2 GiB DDR3


https://github.com/PurpleI2P/i2pd
Independent C++ implementation of I2P router, full C++ implementation of I2P client
http://i2pd.website/?q=en/forum
I2Pd was ported to OpenWRT - https://forum.openwrt.org/viewtopic.php?id=56191
claimed, then it requires only 30-40 MB RAM