Dear Andresrcs, thank you!
R version 3.6.2 (2019-12-12) -- "Dark and Stormy Night"
install.packages ("tm")
--- Please select a CRAN mirror for use in this session ---
also installing the dependency ‘slam’
There is a binary version available but the source version is later:
binary source needs_compilation
slam 0.1-46 0.1-47 TRUE
Do you want to install from sources the package which needs compilation? (Yes/no/cancel)
Before I answered "yes", now I answered "no" ... and it works. Why? 