Small service business with many small cases. Ease of use and FOSS is priority. User is a non-tech person. Amateur tech person (me) will set it up. User uses windows, google sheets and mailchimp for now. looked into:
Vtiger CRM
SuiteCRM
OroCRM
EspoCRM
CiviCRM
Odoo CRM
ERPNext CRM
Perfex CRM
KayinCRM
OpenCRX
OpenERP
SugarCRM Community Edition
They all seem a bit overkill for this.