I was a happy ESS and R user to obtain tex and pdf files from Rnw file with sweave and knitr. I have followed the answer given here, everything worked fine but after several updates or maybe new installation I cannot even find the ess-sweave customization group in Emacs. M-x customize-group: ess-sweave is [No match].
I am using GNU Emacs 25.1.1 on Debian 9 (stable).
> sessionInfo()
R version 3.5.2 (2018-12-20)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Debian GNU/Linux 9 (stretch)
> packageVersion("knitr")
[1] ‘1.21
ESS version is 20190306.2305.
What am I missing to start to use knitr with ESS?