Get admin boundaries as sf objects using {osmdata} package

get-admin-boundaries-osmdata.R

library(osmdata)
library(dplyr)
library(ggplot2)

#Define a place of interest
place <- "Kyiv Ukraine"

#First, get all admin boundaries associated with your request
all_boundaries <- opq(place) %>%
  add_osm_feature(key = "boundary", 
                  value = c("administrative")) %>%
  osmdata_sf() %>% 
  #This next step is optional, depending on what the call returns
  unname_osmdata_sf() %>% 
  .$osm_multipolygons

ggplot(data = all_boundaries) + 
  geom_sf()

#The previous call returns more than one boundary.
#Inspect the data and choose the object you need.
boundary <- all_boundaries %>% 
  filter(osm_id == 421866) %>% 
  #If you're after geometries only, 
  #you won't need all other 200 some columns
  dplyr::select()

ggplot(data = boundary) +
  geom_sf()