Hashcat CPU ethereum pw recovery
Hi Atom, just wanted to report back that I succeeded in installing intel-oneapi-runtime-opencl with your suggestions. Did a test with https://hashcat.net/wiki/doku.php?id=example_hashes and that was successful.
Used ./hashcat.bin  -m15700 -D1 hash.txt pasw.txt
First copied the example hash from the wiki in gedit but then it failed, copying the same in nano did work. Not sure why, gedit should use plain txt as well....
Next thing was extracting the hash from the keystore file used method described here . My keystore file (from 2016) was different than the example (different order), but the information was all there.

Then tried if hashcat recognized the file. Used ./hashcat.bin  -m15700 -D1 hash.txt and it started. Seemed to accept the file but because I didn't add a wordlist it kept on running and I broke it off.

That was the easy part Smile now the real challenge will begin to read about rules and using dictionary/lists and hope that what I remember from the password is enough to retrieve it.  
Tbh - I don't think my chances are very high but I hope hashcat will prove me wrong.
Interesting to read your post. Well done!

I can suggest you the hashcat utils. Combipow is mighty if you remember the words or combinations of your password. It can generate you a list with possible passwords.

Good luck