The R blog moves to https://blog.r-project.org, a more prominent location, after 37 blog posts (some of them perhaps surprisingly detailed) and a bit over 4 years.
This blog site has been started under https://developer.r-project.org in March 2018 as a new communication channel for R developers contributing to the R core implementation. Most of the blog posts cover selected changes in R-devel, the development version of R. They provide a bigger picture for these changes as well as details, ideas, personal experience and opinions of the authors.
The blog site has also been used to inform about upcoming bigger changes impacting R package authors and users. It has been used to ask for volunteers from the R community to help with maintaining the core R implementation. So far this included asking for help with bug reports, to which a number of volunteers responded and helped with analyzing and resolving existing reports. Some new volunteers contributed patches and one eventually joined the R Core Team. More of that help is, and probably always will be, needed. The blog post was also used for asking for help with testing yet unreleased versions of R just before the release, but so far it seems without success.
Some of the blog posts were of interest for developers of other programming language runtimes, such as those about issues in numerical libraries not working with then-recent GNU Fortran due to incorrect calls from C and about transition to UCRT to get UTF-8 as the native encoding on Windows.
The blog complements NEWS, which lists recent changes in core R implementation, mostly one sentence per change, but covers all important and most non-trivial changes. The blog covers a smaller number of selected bigger changes, but in much more detail, with personal opinions, and sometimes even in advance.
Many of active contributors to the R core implementation do not use the blog site much or at all, hence the blogs do not cover some important changes. The blog site hence is not at all a fair measure of coding/maintenance activity happening on the core implementation (one would have to see e.g. the versioning system for that).
The News and notes from the R Journal cover all important changes (so a subset of NEWS) in somewhat more detail and with more background than NEWS, but later after the changes actually happen, with additional statistics on bug/coding activity. The blog has more details, more personal opinions/experience, and covers things just happening or things still only planned.
The R-devel mailing list is a related two-way channel and has been used for follow-ups after at least one of the rather opinionated blog posts. Announcements about most important changes impacting package authors are also sent to that list, and sometimes pointing to more details in a blog post on this site.