Found on a discussion of version control systems on the TUHS mailing list https://www.tuhs.org/pipermail/tuhs/2024-December/031229.html
See also https://neugierig.org/software/blog/2024/12/jujutsu.html for an attempt on an explanation "high-level enough to read and think about, without providing so much detail that it washes over you."
https://ahal.ca/blog/2024/jujutsu-mercurial-haven/ is an article from a Mercurial users.

Work with Git forges, such as Github and Gitlab, from the comfort of Magit and the rest of Emacs.
Found on https://github.com/fstamour/local-gitlab which was mentioned on https://lisp-journey.gitlab.io/blog/i18n-in-my-lisp-web-app-with-djula-templates-and-gettext/

Support for the Fossil version control system https://fossil-scm.org/home/doc/trunk/www/index.wiki for Emacs' VC version control abstraction.

An open source implementation of SCCS, found via https://www.tuhs.org/pipermail/tuhs/2022-June/025898.html
The comparison to RCS on http://sccs.sourceforge.net/sccs_vs_rcs.html appears to be one-sided, but then I am probably biased towards RCS, which was the first version control software I have used.
http://sccs.sourceforge.net/sccs_invention.html sounds like an interesting read.
The last message on the mailing list https://sourceforge.net/p/sccs/mailman/sccs-devel/?viewmonth=201510 I found had been written 2015-10.
According to https://de.wikipedia.org/wiki/J%C3%B6rg_Schilling, the author Jörg Schilling passed away on 2021-10-10.
TODO: find out the license

Game of Trees (Got) is a version control system which prioritizes ease of use and simplicity over flexibility.

Got is still under development; it is being developed on OpenBSD and its main target audience are OpenBSD developers.

Got uses Git repositories to store versioned data. Git can be used for any functionality which has not yet been implemented in Got. It will always remain possible to work with both Got and Git on the same repository.

Pre-commit is a multi-language package manager for pre-commit hooks. You specify a list of hooks you want and pre-commit manages the installation and execution of any hook written in any language before every commit. pre-commit is specifically designed to not require root access.

Found via a link to https://tonsky.me/blog/disenchantment/
on Brett Gilio's article
https://brettgilio.com/posts/2020-07-27-intro-and-computing.html#fn.2

Nikita's article about git is interesting, though a bit old. Note that Fossil implements a web- based GUI.

These simple scripts help in converting an RCS collection of files
into a Git repo.
These scripts are good only for the simple case of a single RCS
directory with no branches, just straight check-ins. Files that
were checked in with a single 'ci' command will be added to git
with a single git commit.

Blog about Unix, C, system administration and more. See for example
https://utcc.utoronto.ca/~cks/space/blog/sysadmin/NotificationsVersusLogs
https://utcc.utoronto.ca/~cks/space/blog/sysadmin/IdentifyMachineEmailByRootName
https://utcc.utoronto.ca/~cks/space/blog/sysadmin/ProceduresAreNotDocumentation
https://utcc.utoronto.ca/~cks/space/blog/sysadmin/RCStoMercurial  Instructions for converting files/directories controlled with RCS to Mercurial.
TODO: mention M-x vc-revision-other-window. Saved Tue 2019-10-29 17:02:29
https://utcc.utoronto.ca/~cks/space/blog/unix/V7WhyItMattersSoMuch  found Mon 2022 -01-10 13:12:03 on https://irreal.org/blog/?p=10149
https://utcc.utoronto.ca/~cks/space/blog/linux/UbuntuKernelAutoremove  MIght want to see whether this is relevant for me. Saved Tue 2017-03-28 19:10:35