This repository contains micropython firmware from various esp32 builds - some I've done myself (esp-now) and others I've just found on github. Do a little research on these builds to determine whether they'll fit your needs. The nickzoic/micropython-esp32 repository was cloned from the original micropython directory at some point. Some of it may have been merged back into the standard "official" micropython esp32 port, but I don't know when.
Here is a list with description:
nowfirmware.bin (USE THIS!!)
Firmware I built from the nickzoic/micropython-esp32/esp32-espnow repo
Firmware I obtained which is the "loboris" micropython repository and it has a number of nice "goodies" in the directory there are flash scripts and a sample command to flash manually.
Firmware I obtained which is the "loboris" mp repository for an ESP32 with psram support. It will work if you don't have psram, but you'll get an error message on boot-up.
Firmware I found online which contains supported releases of mp for the ESP8266 boards.
combined.bin
I believe this is a build from the nickzoic/micropython-esp32 repo that does not contain esp-now support. Don't know what it has more than the standard, supported mp for esp32 releases.
esp32-20190214-v1.10-98-g4daee3170.bin
This is the esp32 build to test my ttgo LoRa boards. Works great but no esp-now support
Firmware I had built by an online service (for free). These are for the esp8266 boards.
nodemcu-master-12-modules-2018-12-02-23-26-21-float.bin
nodemcu-master-12-modules-2018-12-02-23-26-21-integer.bin
A utility to flash esp8266 boards. Google it and get some doc.
ESP8266Flasher.exe