I'm still on Ubuntu 22.04 LTS but needed g++14. The sudo apt-get gcc-14 did not work for me, as it installed clang++14 for some reason (perhaps a misconfiguration on my part). What did work for me was following the instructions I found at https://www.dedicatedcore.com/blog/install-gcc-compiler-ubuntu/

The steps I took:

sudo apt install build-essential
sudo apt install libmpfr-dev libgmp3-dev libmpc-dev -y
wget https://ftp.gnu.org/gnu/gcc/gcc-14.1.0/gcc-14.1.0.tar.gz
tar -xf gcc-14.1.0.tar.gz
cd gcc-14.1.0
./configure -v --build=$(uname -m)-linux-gnu --host=$(uname -m)-linux-gnu --target=$(uname -m)-linux-gnu --prefix=/usr/local/gcc-14.1.0 --enable-checking=release --enable-languages=c,c++ --disable-multilib --program-suffix=-14.1.0
make
sudo make install

And if you would like to make it the default:

sudo update-alternatives --install /usr/bin/g++ g++ /usr/local/gcc-14.1.0/bin/g++-14.1.0 14
sudo update-alternatives --install /usr/bin/gcc gcc /usr/local/gcc-14.1.0/bin/gcc-14.1.0 14

After that, g++ showed I was running version 14.1.0. I was then able to compile my project that included some c++20/23 features that were not in the previous versions of g++ (chrono/format).

If you want to install it as a local user

GNU GSRC provides an easy way to do so

Link: http://www.gnu.org/software/gsrc/

After configuration, simply specify the following commands:

Copycd gsrc
make -C pkg/gnu/gcc 
make -C pkg/gnu/gcc install

The second step could also be changed to speed up for an N-core system:

Copymake -C pkg/gnu/gcc MAKE_ARGS_PARALLEL="-jN"

If you don't change any settings, it should be fine. It will install to /usr/local, which will keep it separate from that platform's default gcc installation.

You may want to give the configuration tool a "program suffix" option to give it a name based on the version.

I would start by doing a gcc -v to see what options your platform's default GCC build uses, and consider each of those options to see if you want to include them. Do not change any of the default directories as your platform default did though. You want it to go into /usr/local.