Here we are on release 19.14, we were successful but our experience was like this:
First I did a request test using the conventional wallet to ensure that the certificate was not in the wallet and, therefore, would return the error ORA-29024:Certificate Validation Failure.
select utl_http.request('https://web.whatsapp.com', null, 'file:/u1/oradata/dev/wallet') x from dual
Next, I tested the same request using the wallet based on the operating system "system:". At this point, we got "ORA-29248: an unrecognized WRL was used to open a wallet" error.
select utl_http.request('https://web.whatsapp.com', null, 'system:') x from dual
At that time, I also imagined that it was because we were not on a newer release of the database.
A few days later, luckily, I repeated the test. But this time, I didn't make the first request with the conventional wallet as before, I went straight to the wallet based on the operating system. And to my surprise, it worked!
I then made the request for the conventional wallet again and got ORA-29024 in the same session. After this error, any request in the same session with the "system:" wallet shows the error "ORA-29248: an unrecognized WRL was used to open a wallet."
With this, I was able to conclude that, since Oracle loads the conventional wallet into memory, it is not possible to use the wallet based on the operating system in the same session.
You may double check if you have the conventional wallet being set in some point in your session leading you to the ORA-29248 error.