Via Sigma (rule format for SIEM's) converters, it is possible to convert Sigma rules to Splunk queries.
This is a well established process and can be done through tools like: https://github.com/SigmaHQ/pySigma
or https://github.com/SigmaHQ/sigma
My question is, is there any way to do the reverse?
Is there a way to convert Splunk queries into Sigma Rules?
In case this is still a topic: https://www.patrick-bareiss.com/sigma2splunkalert-tutorial/
As with any such abstract tools, I'd advise strongly against using it.
I tested the sigmac some time ago and it produced an extremely ugly searches and didn't support a huge subset of the sigma rules specification.
I also doubt that fairly useful functionality the opposite way (splunk to sigma rules) is possible. Maybe for some small subset of spl commands and constructs but - as the infamous example of "spl for sql users" shows, automatic translation is simply producing bad results.
You are right....I normally use the Sigma searches as inspiration and use them to create and tailor a search for my own environment and specific needs. You need to look beyond the ugliness of the translation and find the detection gems in them.
I always user www.uncoder.io but that does not work from Splunk to Sigma unfortunately.