We choose to work with the Raspberry Pi Pico microcontroller board, in part because of the ease with which the firmwear can be updated by the end user. If you have a compiled program in .UF2 format, it can be loaded on the pico using a "drag and drop" technique, just like moving a file from one folder to another.
To begin the process, unplug your Pico from your computer and re-plug it in while holding down the "BOOT SEL" button. The Pico will then appear on your computer as a USB memory drive. Note that a number other microcontroller boards can be programmed in a similar way. Adafruit produces a number of these using SAMD chips. Here is an introduction.
Once you have your sketch working as you want it, you can create a .UF2 file which will make flashing to multiple devices faster and easier. To do this you will need the MakeUF2 plugin. You can download the plugin from here.
Once you have the plugin installed, you first need to export your sketch as a binary file. To do this, go to Sketch > export compiled binary.