Changing the domain registrar doesn’t really have anything do to with SEO (probably why you couldn’t find a similar question).
When you change registrar you are changing the organisation through which the domain is registered, that is all. The DNS does not necessarily change. However, if the DNS is also managed by the registrar then you will need to make sure that the appropriate DNS records are also configured at the new DNS host/registrar.
As far as the end user (and search engine bot) is concerned, nothing has changed. So, no change in SEO.