How to autoplay a Plotly chart in Shiny?

I have the following Shiny app with two animated barplots in plotly. I want them to play automatically upon loading (as in here, for instance). I need them to play only once (hopefully at the same time), just to give the impression that the bars "load", after that I don't need them to be animated anymore, so I'll have the buttons hidden.

This answer shows a complicated (for me) way of doing so which I have not been able to adapt to my app. However, it mentions that "animation might not actually be necessary for this example since the data points are not moving.", which might work for me as the relevant value of my_df is only the first observation (which corresponds my last frame, as the other frames were only added to animate the bar).

I've also found this plotly.github.io entry where they mention a function with an auto_play argument which seems to do what I need, but I don't know where or how to use it.

In case it helps anyone come up with a solution I list here a couple posts with related questions (this one is for dash-python, and in this one the OP asks for a way to press play using a shiny action button - which might help figure out a way of programmatically trigger the animation).

Any of the options (autoplaying, triggering the animation programmatically or a solution not involving plotly animation) works for me.

Here's my code:

library(shiny)
library(plotly)


my_df <- data.frame(
    vals = c(39, 0, 3.9, 7.8, 11.7, 15.6, 19.5, 23.4, 27.3, 31.2), 
    indic = rep("A", times = 10), 
    frame = c(10, 1, 2, 3, 4, 5, 6, 7, 8, 9))

ui <- fluidPage(plotlyOutput("first_plot", width = "50%"),
                plotlyOutput("second_plot", width = "50%"))

server <- function(input, output, session) {
    output$first_plot <- renderPlotly({
        plot_ly( data = my_df, y = ~indic, frame = ~frame, type = "bar", height = 200) %>% 
            add_trace(x = ~vals) %>% 
            layout(barmode = "stack") 
    }) 
    output$second_plot <- renderPlotly({
        plot_ly( data = my_df, y = ~indic, frame = ~frame, type = "bar", height = 200) %>% 
            add_trace(x = ~vals) %>% 
            layout(barmode = "stack") 
    }) 
}

shinyApp(ui, server)

You can run the animation with JavaScript with the help of the onRender function. The animation will be played whenever the chart is rendered.

library(plotly)
library(htmlwidgets)

df <- data.frame(
  x = c(1,2,1), 
  y = c(1,2,1), 
  f = c(1,2,3)
)
df %>%
  plot_ly(
    x = ~x,
    y = ~y,
    frame = ~f,
    type = 'scatter',
    mode = 'markers',
    marker = list(size = 20),
    showlegend = FALSE
  ) %>% 
  animation_button(visible = TRUE) %>%
  onRender("
        function(el,x) {
          Plotly.animate(el);
        }")