What are the best practices for keeping and analyzing unstructured user feedback?

To get and analyze users' feedback is vital for designing successful products as all of you perfectly know. It is more or less clear what to do with surveys' results, but what is the best way to keep results of interviews and unstructured user reports?

Shame but now I just keep feedback in a special mailbox and store interviews' summary in Notes. As a result, I create tickets in Jira after short analysis :) Previously when I had 3 more designers we used spreadsheets (excel, confluence, google sheets) but it takes too much time now when I'm the only designer (yet). The main issues with those approaches are:

• you can't really analyze anything (e.g. find alike or controversial things) in Notes and mail ))
• spreadsheets give some sort of analysis capabilities but it consumes too much time

Any hints on how to avoid spreadsheets? Thanks!