Cleanup license information throughout the projects
Right now licensing information is rather fragmented: some files use SPDX, others don't, different license headers in the same project etc.
There's handy tool https://reuse.software/ which could help remediate this.
Running 'reuse lint' in the repository (installable via 'sudo apt install reuse') will give comprehensive report regarding project licensing information.
Once outstanding issues are fixed, it can be added to commit linter to make sure the compliance is checked automatically.