can you list the options to use regex in an unknown json file?

Perhaps we could convert to a data.frame and then subset

library(jsonlite)
library(dplyr)
library(purrr)
library(stringr)
fromJSON(myjson) %>% 
    invoke(data.frame, .) %>%
    filter(select(cur_data(), where(is.character)) %>%
                   map(~ str_detect(., 'station')) %>% 
                   reduce(`|`)
           )

-output

#   time  id user.id   user.game user.hobby
#1 today 123     456 playstation       <NA>
#2 today 555      42        play    station

If the data is heavily nested, there is a flatten argument in fromJSON which is by default FALSE

fromJSON(myjson, flatten = TRUE) %>%
     filter(select(cur_data(), where(is.character)) %>%
                   map(~ str_detect(., 'station')) %>% 
                   reduce(`|`)
           )

-output

#   time  id user.id   user.game user.hobby user.user.id user.user.game user.user.hobby
#1 today 123     456 playstation       <NA>           NA           <NA>            <NA>
#2 today 555      42        play    station           10           play         station