Jasper is minimalistic, easy to use customer relationship management software for small business. All local to your device. Your data belongs to you.
Guide: https://variatur.au/jasper/guide/
Features:
Customers - each customer contains name and location details
Notes - each customer has a list of notes, you can use this to store anything but common uses are contact log history and sales history.
Reminders - If you have to contact or do something for a customer on a certain date, you can set a reminder! All due reminders are shown on the right of your screen, sorted by due date.
Tags - If you want to group customers, create and assign a tag to them! You can search for these tags in the customer search.