ggplot2 issue with default font size (base_family = "") - r

Question

As you can see in this post someone found the solution to my problem where the text in my ggplot2 graphs were replaced by unicode-blocks. This was caused by an error in the default font settings of ggplot2 (base_family = ""). Therefore, the workaround was to manually set the base_family argument to "Arial".
Here you can see an example code:
# Libraries
library(ggplot2)
# create data
xValue <- 1:10
yValue <- cumsum(rnorm(10))
data <- data.frame(xValue,yValue)
# Plot
ggplot(data, aes(x=xValue, y=yValue)) +
geom_line() +
theme_classic()
The resulting graph looks like this where the text is shown in weird unicode blocks (sorry I do not know what these are called exactly):
I can manually solve the issue by setting the theme base_family to "Arial":
# Libraries
library(ggplot2)
# create data
set.seed(42)
xValue <- 1:10
yValue <- cumsum(rnorm(10))
data <- data.frame(xValue,yValue)
# Plot
ggplot(data, aes(x=xValue, y=yValue)) +
geom_line() +
theme_classic(base_family = "Arial")
This is the image of the resolved issue, which only works if the base_family is set to a specific font like "Arial":
The question is why does my system somehow conflict with the default font and how can I set the default font back to normal? Because now I have to call the base_family = "Arial" Argument in every plot I make with ggplot2. I should mention, that I have no font issues with e.g. plotly whatsoever. I have not found any similar problems except a link on how to change the default setting for a specific theme type but I would like to reset the settings back to normal so base_family = "" works again. I hope you can help me out and please do not hesitate if you need further information from me.
R version: 3.6.1 (2019-07-05)
platform: linux mint x86_64
conda environment

Answer 1

Thanks to #tjebo I was able to resolve the issue by upgrading my R version to 4.0.3. and switched to ipython notebook since as far as I understood R-Studio does not support version 4.0.3 (EDIT: probably only an issue caused by conda and not by R-Studio).
I work with conda and therefore I created a new environment
# Create and activate conda environment
conda create --name r4
conda activate r4
Then I installed the R Verison 4:
# install R version 4
conda install -c conda-forge r-base
conda install -c conda-forge/label/gcc7 r-base
Finally, I installed irkernel in order work with R in IPython notebooks:
# Install R kernel for IPython notebook
conda install -c r r-irkernel
IRkernel::installspec()
# open jupyter notebook
ipython notebook
Inside the ipythone notebook I could now choose "R" as a kernel and the code I previously had issues with works as expected. Again credits to #tjebo.
EDIT: Reinstalling R lead to further issues where packages were not beeing installed correctly due to missing lib files. But this is offtopic so I will probably open another discussion somewhere else. (FYI Link to the solution was postet by #fredaas here)