sudo apt-get install build-essential asciidoc binutils bzip2 gawk gettext git subversion libssl-dev libncurses5-dev patch unzip zlib1g-dev libc6-dev libbz2-dev gdisk flex python3-distutils
sudo apt-get install libc6:i386 libgcc1:i386 libstdc++5:i386 libstdc++6:i386 libc6-dev-i386
sudo apt-get install intltool
sudo apt-get install tk-dev libffi-dev liblzma-dev libreadline-dev libsqlite3-dev
For python3.6+,we can use pyenv:
git clone https://github.com/pyenv/pyenv.git ~/.pyenv
echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bashrc
echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(pyenv init -)"' >> ~/.bashrc
exec $SHELL -l
pyenv install 3.9.10 -v
pyenv rehash
pyenv global 3.9.10
wget http://ftp.gnu.org/pub/gnu/libiconv/libiconv-1.13.1.tar.gz
tar zxvf libiconv-1.13.1.tar.gz && cd libiconv-1.13.1
./configure --prefix=/usr/local
make
sudo make install
sudo make install && sudo ln -s /usr/local/lib/libiconv.so /usr/lib
sudo ln -s /usr/local/lib/libiconv.so.2 /usr/lib/libiconv.so.2
./scripts/feeds update -a
./scripts/feeds install -a
make menuconfig
make V=99