The default for the r_version argument of backport_linter() is getRversion(), which, in most case, won't provide any useful insights.

A possibly better default in the case of R package, or any project with a DESCRIPTION file, would be to extract the stated minimum R version and use it.

This means that backport_linter() would now automatically warn you if you use a function that has been defined in an earlier R version that what you declared in DESCRIPTION.

This can be done with a handful of base R function:

depends <- read.dcf("DESCRIPTION", "Depends")

depends_list <- trimws(unlist(strsplit(",")))

depends_r <- grep("R ", depends_list, value = TRUE)
min_r_version <- gsub("^R \\(>=?\\s(.+)\\)", "\\1", depends_r)

An alternative that seems less generic but still more informative than the default could be to use the tidyverse policy of supporting oldrel-4. This can make sense since the rest of the lintr already defaults to the tidyverse policy.