I have tried to install Bioconductor. I have a functioning version of R (R version 4.0.0 (2020-04-24) -- "Arbor Day" using the following from the Bioconductor website

if (!requireNamespace("BiocManager", quietly = TRUE))
  install.packages("BiocManager")
BiocManager::install(version = "3.11")

Here is what I got back.

Bioconductor version 3.11 (BiocManager 1.30.10), R 4.0.0
  (2020-04-24)
Installation path not writeable, unable to update packages:
  boot, class, foreign, KernSmooth, MASS, nlme, nnet, spatial
>

The listed packages are 'recommended' packages that were probably installed when R itself was installed. They were likely iinstalled by an 'administrator' account, and cannot be updated by a regular user.

I would recommend fixing the underlying problem. As administrator, remove the recommended packages. Re-install the recommended packages as a regular user. BIocManager will then continue to update these as updates become available.

If this is not possible, then I recommend simply ignoring the message that the recommended packages are not writeable.