Curious how small businesses here track leads and sales day to day

Quick question for the business owners here: how do you currently track leads and sales? Spreadsheet, notebook, Messenger, a CRM, or just memory?

I ask because I'm building a lightweight sales tracker (iSerbe) for small/medium businesses, and I keep finding that people either overpay for a bloated CRM or just wing it with Sheets. Trying to figure out where the real gap is before I keep building. Would love to hear what's worked or not worked for you.