How do I downgrade Pi 4B bootloader/firmware?

How do I downgrade the Pi 4B bootloader from 2021-04-29 to 2020-09-03?

I was able to get the 2020-09-03.bin file from Github, but I'm not sure how to install it and I've search all over Google trying to figure it out.

Reason I want to downgrade:

I have a old Pi 4B 8GB running LibreElec 9.2.6 and it's perfect.

I got a new Pi 4B 8GB and a new SD card and put LibreElec 10.0.1 on it but found there were too many apps that weren't available for it (Python 3). So I reimaged the card to 9.2.6 and the new Pi won't boot it.

I tried that new card (with 9.2.6) in my old pi and it boots every time, so I know the card and image are good. I put the card back to 10.0.1 and it boots in the new pi.

So it seems that the new pi will not boot 9.2.6. Only thing I can think of is the bootloader updated to 2021-04-29 when I first tried 10.0.1 in it. So I want to downgrade it to 2020-09-03 like my old pi has to see if that will fix it.

Thanks!

Quote from Da Flex

Firmware gets updated during LE's installation process. That's why DJ'ing LE cards fails.

Ya, I think that's my issue. When I put in 10.0.1 it updated the firmware, but the new firmware doesn't like to boot the older LE 9.2.6.

I'm hoping rolling back will fix it. Either that or it's something hardware related to pi rev 1.4.

Quote from Klojum

Well... It was announced only some 2.5 years ago that the Python part of Kodi would be upgraded from v2 to v3. If developers still haven't found the time to upgrade their Kodi add-ons, then that's on them.

Which add-ons (apps..) are still not available for Kodi 19?

When I pulled in my Kobi backup to 10.0.1 there were a lot of my apps that said there were disabled. I ran the updates and some came back but a lot didn't. I don't remember exactly which ones but there were so many I want to stay on 9.2.6 for now because it works perfect.

Hopefully there's a way to rollback and it works. I've found a number of posts here with people that have the same issue with rev 1.4 Pis. you get a solid white _ symbol in the top left corner when booting 9.2.6. But no one posted that they solved it or how/if there were able to downgrade the bootloader.

Quote from Da Flex

Raspberry Pi OS has a tool to install firmware manually.

Perfect. I'll check that out. Thank you

Quote from ghtester

I wouldn't do it but it's up to you... Try this:

Code

cd /tmp
wget -O pieeprom.bin -c https://github.com/raspberrypi/rpi-eeprom/raw/master/firmware/stable/pieeprom-2020-09-03.bin
rpi-eeprom-config pieeprom.bin > bootconfDefault.txt
# default config
cat bootconfDefault.txt
vcgencmd bootloader_config > bootconf.txt
# current config
cat bootconf.txt
rpi-eeprom-config /tmp/pieeprom.bin --config /tmp/bootconf.txt --out /tmp/pieeprom
rpi-eeprom-update -d -f /tmp/pieeprom
reboot
#

Display More

Please note you may need to change the bootloader config as there're some changes in recent bootloader revisions.

Thank you. Why wouldn't you do it? Could I brick my Pi?

If it doesn't fix the issue can't I just put LE 10.0.1 in again and have it update the bootloader?

Thanks

Quote from ghtester

Hopefully you won't brick your RPi 4B (even though you install a bad bootloader and your RPi 4B does not boot, it's possible to create a recovery micro SD card which can fix it) but I think it won't help you.

Please note the firmware (which is located on LE filesystem) must support the RPi 4B hardware release. As RPi 4B v. 1.4 is newer than LE 9.2.6 build (and there are significant HW differencies between old and new RPi 4B revisions), it probably won't work with new RPi 4B as the firmware in LE 9.2.6 is simply too old. So you may try to replace the firmware files on LE 9.2.6 filesystem but who knows if it ever helps...

Instead I would upgrade the bootloader to latest stable (pieeprom-2021-12-02.bin) and run LE >= 10.

Thanks so much for the reply. I didn't realize HW differences in rev 1.4 affected the bootloader and LE9.2.