This is my proposal for concrete actions:

• fork the labs/toollabs.git repo into a more modern namespace, probably something like toolforge-utils.git
• consider if we really need to have native debian packages, i.e, separate main source code development from debian packaging itself
• create a modern repository layout taking into account previous points in this checklist (i.e, support for different distros? which git branches are going to use? workflow may change a bit if using a non-native package)
• drop debian/ and start from scratch, probably easier than doing it incrementally, adapted to modern debian workflows (gbp, sbuild, debhelper, etc)
• ensure the package/repo has enough jenkins coverage and is the package is left in a clean state regarding jenkins testing
• document all this new stuff!

Some of these points may need conversations with people somehow involved with the code (@bd808, @zhuyifei1999, @Legoktm, among others).
My estimation of full time requirement to address all this is about 1-2 days in the worst case once all has been decided and agreed, if we don't find any bad surprises along the way.

I don't plan to work on this in the short term unless the team decides otherwise.

jmail has been deprecated in T208579 can possibly be removed.

Same reworking may be applied to the tools-manifest package.