Ok the link below may not be much better than the one you’ve shown, I’ll have a look at that soon.
EDIT The post states " You can do that in Settings / Storage / SD card / Apps. You have to move each app individually."
So looking at the SD card will not help.
Default apps would be on the internal memory but any you downloaded may be on the SD card…
if you have difficulty you may want to reset the phone but you will loose any data you have collected so at least backup your contacts and export them and transfer your images etc to another device.
Anyway have a look at