To build EiskaltDC++ with unicode support on Ubuntu, you need to do just a few simple steps...
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First install base repo client and update:

sudo apt install eiskaltdcpp

git clone https://github.com/eiskaltdcpp/eiskaltdcpp

sudo apt install cmake

cd eiskaltdcpp

mkdir builddir

cd builddir

sudo apt install libssl-dev libpcre3-dev libidn2-dev liblua5.2-dev liblua5.3-dev libminiupnpc-dev libqt5*dev qttools5-dev qtmultimedia5-dev libpspell-dev

cmake ..

make

sudo make install

[Done]