I precisely followed the instructions at

https://github.com/LadybirdBrowser/ladybird/blob/master/Documentation/BuildInstructionsLadybird.md

and it failed for two reasons; the second of which I could not solve.

1. Adding the repository and GPG key calls lsb_release -sc, which returns “virginia” here, instead of “jammy” which it is based on. → This was easy to solve, by editing sed 's/virginia/jammy/g' /etc/apt/sources.list.d/llvm.list. Yes, the instructions say Ubuntu, and not Mint. But this is the first time that claused problems, and since Mint is more popular AFAIK, it’s probably a good idea to support it. Should be easy too.
2. After continuing to follow the instructions with the fixed codename, ./Meta/ladybird.sh run ladybird fails too, because according to ./Toolchain/Build/cmake/Bootstrap.cmk/cmake_bootstrap.log, cmake_bootstrap_109383_test.cxx:2:10: fatal error: 'iostream' file not found.

Here’s the full log: cmake_bootstrap.log

I’m not a C++ programmer, so I have no idea why it can’t find iostream.