About 4 months ago I helped adding support for the ST7789 320x240 SPI TFT display to the PiTFT helper installer script. I recently updated RaspberryPi OS (and also tried a fresh install) and had trouble getting the ST7789 320x240 TFT display to work again.
Apparently, the latest system updates also updated the Linux kernel from version 4.19 to version 5.4. Unfortunately the PiTFT installer script didn't work with this linux kernel anymore, because fbtft_device and flexfb are gone in 5.4 A new device tree overlay for the st7789 displays was required from now on.
I reported the issue on GitHub and over the next few days I helped troubleshoot, made suggestions for revising and optimizing the code and did a lot of test installations using the PiTFT helper script. You can read the whole story in the GitHub issue:
Long story short: The “PiTFT helper” script was fixed and the installation works again.
Installation steps: Mirroring HDMI with fbcp to the TFT screen
Note: With the new version, the boot process is no longer displayed on the TFT, so there is no splash screen visible on the TFT. The TFT remains black until the X desktop is available.