How to combine multiple R modules (with submodels and uiOuput) using shinydashboard?

Question

I'm modularizing a Shiny app I developed using shinydashboard packages. Despite it traditionally works when I use it without involving modules, I can't make it work when I try to divide it into modules and submodules. Here I would like to combine two UIs (one for the sidebar, one for the body) in order to upload a dataset from the sidebar and show it into the body. I'd be very glad if anybody could provide me some help with this.

Here is the code of the general Shiny app:

library(shiny)
library(excelR)
library(vroom)
library(readxl)
library(janitor)
library(dplyr)
library(shinydashboard)
library(shinydashboardPlus)

# # load separate module and function scripts
source("modules.R")

# app_ui 
app_ui <- function() {
  tagList(
    shinydashboardPlus::dashboardPagePlus(
      header = shinydashboardPlus::dashboardHeaderPlus(title = "module_test",
                                                       enable_rightsidebar = FALSE),
      sidebar = shinydashboard::dashboardSidebar(
        shinydashboard::sidebarMenu(id = "tabs",
                                    import_sidebar_ui("import"))
      ),
      body =  shinydashboard::dashboardBody(shinydashboard::tabItems(
        import_body_ui("import"))
      ),
      rightsidebar = NULL,
      title = "Module App"
    )
  )
}
# app_server 
app_server <- function(input, output, session) {
  shiny::moduleServer(id = "import", module = import_server)
}


####################################################################
run_app <- function(...) {
  shiny::shinyApp(
    ui = app_ui, 
    server = app_server)
}
#---------------------------------
run_app()

and here is the modules.R file I wrote containing the UIs for sidebar and body, plus the server:

# Import module ####
# 
# Import sidebar UI
import_sidebar_ui <- function(id) {
  ns <- NS(id)
  shinydashboard::menuItem("Module Testing",
                           tabName = "tab_testing_mod",
                           icon = icon("th"),
                           tagList(
                             selectInput(ns("input_type"),
                                         "Type of file:",
                                         choices = c("Choose one" = "",".csv" = "csv",
                                                     ".txt" = "txt", ".xls/.xlsx" = "xlsx"),
                                         selected = NULL),
                             uiOutput(ns("inputControls")),
                             fileInput(ns("file"), "Data", buttonLabel = "Upload..."),
                             checkboxInput(ns("rownames"), "Check if 1st column contains rownames"),
                             checkboxInput(ns("constant"), "Remove constant columns?"),
                             checkboxInput(ns("empty"), "Remove empty cols?"),
                             actionButton(ns("bttn_import"), "Import data")
                           )
  )
}

# Import body UI
import_body_ui <- function(id) {
  ns <- NS(id)
  shinydashboard::tabItem(tabName = "tab_testing_mod",
                          fluidRow(
                            h3("Imported Data"),
                            excelR::excelOutput(ns("preview")))
                          )
}

# Import server
import_server <- function(input, output, session) {
  ns <- session$ns

  output$inputControls <- renderUI({
    tagList(

      switch(input$input_type,
             "csv" = textInput("delim", "Delimiter (leave blank to guess)", ""),
             "txt" = textInput("delim", "Delimiter (leave blank to guess)", "")
      ),
      switch(input$input_type,
             "xlsx" = numericInput("sheet", "Sheet number", value = 1))
    )
  })

  raw <- reactive({
    req(input$file)

    if (input$input_type == "csv" || input$input_type == "txt") {
      delim <- if (input$delim == "") NULL else input$delim
      data <- vroom::vroom(input$file$datapath, delim = delim)
    } else if (input$input_type == "xlsx") {
      data <- tibble::as.tibble(readxl::read_excel(input$file$datapath, sheet = input$sheet, col_names = TRUE))
    } else {
      return(NULL)
    }
    raw <- data
    raw
  })

  tidied <- eventReactive(input$bttn_import,{
    out <- raw()
    if (input$empty) {
      out <- janitor::remove_empty(out, "cols")
    }
    if (input$constant) {
      out <- janitor::remove_constant(out)
    }
    if (input$rownames) {
      out <- tibble::column_to_rownames(out, var = colnames(out[1]))
    }

    out <- out %>% dplyr::mutate_if(is.character,as.factor)

    out
  })

  output$preview <- excelR::renderExcel({
    excelR::excelTable(data = raw(),
                       colHeaders = toupper(colnames(raw())), 
                       fullscreen = FALSE,  
                       columnDrag = TRUE,  
                       rowDrag = TRUE,
                       wordWrap = FALSE,
                       search =TRUE,
                       showToolbar = TRUE,
                       minDimensions = c(ncol(raw()),10)
  )
  })
}

It seems to me I can upload the dataset (.csv, .txt or .xlsx) files but I can't show it into the body. I'd be very glad if you can help me, thank you very much in advance for your assistance.