seeking: task request utility for Linux Mint laptop

Will someone please suggest a FOSS application for Linux Mint 19.3 and later or Ubuntu 20 workstations?

I'm familiar with Request Tracker and like many of its features. However, it seems
too bulky/heavy for an individual workstation.

The application I seek is mostly a TODO-list with some extra features.
Here are some of my wish-list items:

• send notifications as reminders of due dates and times
• receive email to queue tasks and reminders and similar
• all data storage local to the workstation
• "sharing" of data with other copies of the application suite some what other than export/import
• native application or workstation hosted web server implementation
• support multiple projects for multiple clients
• support multiple users on the same workstation

Thanks in advance,
~~~ 0;-Dan