[R] R installation Ubuntu 10.04 missing dependency

[John Kane]

To upgrade to R.3.5.2 from 3.4.4 I have been following the
instructions at
https://www.r-bloggers.com/installation-of-r-3-5-on-ubuntu-18-04-lts-and-tips-for-spatial-packages/
.

I seem to have the repository properly connected and verified.

I am getting an error:
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john using jonh-T510:~$ sudo apt install r-base r-base-core r-recommended
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help resolve the situation:

The following packages have unmet dependencies:
 r-base-core : Depends: libreadline6 (>= 6.0) but it is not installable
               Recommends: r-base-dev but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
-------------------------------------------------------------------------------------------------
Earlier I was getting another error
r-base-core : Depends: libpng12-0 but it is not installable
but that was cured by installing libpng12-0 via the Ubuntu Software app.

I cannot find what appears to be an installable version of libreadlines6.

Ubuntu reports that the up-to-date version of libreadlines7.

Should I consider this an R issue or an Ubuntu issue?

In any case, has anyone encountered the problem and beaten it?

Thanks

-- 
John Kane
Kingston ON Canada