Every language is a separate project. Any year, day and part can be run with command line arguments.
For example, to run the Rust 2023 day 1 part 1 solution, do cd rust; cargo run -- run -y 2023 -d 1 -p 1.
To run the Elixir 2024 day 1 part 1 solution, do cd elixir; mix aoc.run -y 2024 -d 1 -p 1.
Input *.txt files are excluded because the creator of Advent of Code has requested not to include them.
Source: https://twitter.com/ericwastl/status/1465805354214830081
Instead, follow the examples for each language for including input files.