Homebrew is for Linux and macOS, allowing install of the latest compilers and other packages without sudo.
Use the Homebrew install script without sudo.
Install desired packages such as Gfortran:
brew install gcc
Generally the latest compilers are available from Homebrew for Linux and macOS.
Instead of putting Homebrew environment variables into ~/.profile, consider putting them into
~/brew.sh, where you can activate them when needed, instead of constantly being active.
Either choice is fine of course.
PATH="/home/linuxbrew/.linuxbrew/bin:$PATH" MANPATH="/home/linuxbrew/.linuxbrew/share/man:$MANPATH" INFOPATH="/home/linuxbrew/.linuxbrew/share/info:$INFOPATH" HOMEBREW_EDITOR="nano"
To use Homebrew, type
Upon closing the terminal, the configuration falls back to default (non-Homebrew)