Anconda R version - How to upgrade to 4.0 and later
You need to create a new environment and then you can install R 4.+ in Anaconda. Follow these steps.
conda create --name r4-base


After activating r4-base run these commands
conda activate r4-base
conda install -c conda-forge r-base
conda install -c conda-forge/label/gcc7 r-base

Finally, you will notice r-basa version 4 will be installed.

Thereafter, you can install any supported packages. But with this only, you won't have the ability to use it in the Jupyter notebook. You need to install install.packages('IRkernel') and Jupyter notebook as well if you want to use it. Otherwise you are good to go with R-Studio.
For Jupyter Installation and RKernel.
conda install jupyter

Then open the R console. Write in R console
install.packages('IRkernel')
IRkernel::installspec()

Congrats! You can use Notebook for Python and R.