I remember having to install a 3rd party program on an old Android phone to move things to the SD card. The OS would barely touch anything itself, even if you told it to.
I think the program I used was called App2SD, but that was in Android v4 or around there. I don't know how or if such a thing would work on more modern versions now.
Edit: It was Link2SD, not sure if it's suitable anymore, recent reviews say it doesn't work, and to use something else. I think it's outdated now, but it worked great when I used it back then.
There are certainly other programs with the same features with better reviews, that you could try.
I think the program I used was called App2SD, but that was in Android v4 or around there. I don't know how or if such a thing would work on more modern versions now.
Edit: It was Link2SD, not sure if it's suitable anymore, recent reviews say it doesn't work, and to use something else. I think it's outdated now, but it worked great when I used it back then.
There are certainly other programs with the same features with better reviews, that you could try.