I have about 0 experience with openssl, I just looked at the man page (openssl-enc). It looks like this command doesn’t take a positional argument. I believe the etcBackup.key file isn’t being read, as that command simply doesn’t attempt to read any files without a flag like -in or -out. I could be wrong though, see previously stated inexperience.
I’ve had good experiences with whisper.cpp (should be in the AUR). I used the large model on my GPU (3060), and it filled 11.5 out of the 12GB of vram, so you might have to settle for a lower tier model. The speed was pretty much real time on my GPU, so it might be quite a bit slower on your CPU, unless the lower tier models are also a lot faster (never tested them due to lack of necessity).
The large model had pretty much perfect accuracy (only 5 or so mistakes in ~40 pages of transcriptions), and that was with Dutch audio recorded on a smartphone. If it can handle my pretty horrible conditions, your audio should (hopefully) be no problem to transcribe.