Hugo 0.55.x theme warnings from newly created blogdown sites

After a regular successful hugo/blogdown installation:

devtools::install_github("rstudio/blogdown")

I'm getting the following avoidable warnings, most likely due to an outdated hugo-lithium theme?:

$ hugo version
Hugo Static Site Generator v0.55.6/extended darwin/amd64 BuildDate: unknown
$ hugo
Building sites … WARN 2019/06/12 10:23:34 Page's .Hugo is deprecated and will be removed in a future release. Use the global hugo function.
WARN 2019/06/12 10:23:34 Page's .URL is deprecated and will be removed in a future release. Use .Permalink or .RelPermalink. If what you want is the front matter URL value, use .Params.url.
WARN 2019/06/12 10:23:34 Page's .RSSLink is deprecated and will be removed in a future release. Use the Output Format's link, e.g. something like:
    {{ with .OutputFormats.Get "RSS" }}{{ .RelPermalink }}{{ end }}.
(...)

Other relevant info for this issue:

> xfun::session_info('blogdown')
R version 3.6.0 (2019-04-26)
Platform: x86_64-apple-darwin18.5.0 (64-bit)
Running under: macOS Mojave 10.14.5, RStudio 1.1.463

Locale: C

Package version:
  BH_1.69.0.1     R6_2.4.0        Rcpp_1.0.1      base64enc_0.1.3 blogdown_0.13.1
  bookdown_0.11   digest_0.6.19   evaluate_0.14   glue_1.3.1      grDevices_3.6.0
  graphics_3.6.0  highr_0.8       htmltools_0.3.6 httpuv_1.5.1    jsonlite_1.6   
  knitr_1.23      later_0.8.0     magrittr_1.5    markdown_1.0    methods_3.6.0  
  mime_0.7        promises_1.0.1  rlang_0.3.4     rmarkdown_1.13  servr_0.14     
  stats_3.6.0     stringi_1.4.3   stringr_1.4.0   tinytex_0.13    tools_3.6.0    
  utils_3.6.0     xfun_0.7        yaml_2.2.0     
Warning message:
Character set is not UTF-8; please change your locale

> remotes::install_github('rstudio/blogdown')
Skipping install of 'blogdown' from a github remote, the SHA1 (d26e72ff) has not changed since last install.
  Use `force = TRUE` to force installation

By filing an issue to this repo, I promise that

[x] I have fully read the issue guide at https://yihui.name/issue/.
[x] I have provided the necessary information about my issue.
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- If I'm filing a bug report, I have included a minimal, self-contained, and reproducible example, and have also included xfun::session_info('blogdown'). I have upgraded all my packages to their latest versions (e.g., R, RStudio, and R packages), and also tried the development version: remotes::install_github('rstudio/blogdown').
- If I have posted the same issue elsewhere, I have also mentioned it in this issue.
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rstudio / blogdown

Hugo 0.55.x theme warnings from newly created blogdown sites #389