You can search for these packages on CRAN to see if they're available, and if so, for which version they have last been built.
Searching shinyapps yields this, which indicates there's no package on CRAN by that name. Compare this with ggplot2, which yields this as its first result.
There are generally two common cases for the "not available for R version xyz"-error:
- The package has not been built on CRAN for your R version and operating system yet (for 3.6.0, I think most packages should be built by now for most OSes)
- The package is from a non-CRAN repository, like GitHub or RForge (looking at the
RForgeTools in your list there). This is probably the case for the shinyapps and rstudio packages.
You might want to search Github for these packages names. For shinyapps, I get this repository from RStudio which says it's a deprecated package an replaced by rsconnect, so as long as you have rsconnect installed, you can probably safely ignore that package.
For the htmldeps package, you'll find that https://github.com/rstudio/htmldeps – I think you have this installed as a dependency for a different package, maybe shiny? Anyway, if you install the package that depends on htmldeps again, it should also install it's dependencies from GitHub if they were declared appropriately. Alternatively you can remotes::install_github("rstudio/htmldeps") if you know you need it.