[Realme 6 Questions & Answers] AT9M:
Hello

I don't think the issue you have is because of recovery not supporting android version. The thing you are saying(oplus verify fail need to verify signature of another brand) is bootloader. I think the reason it goes to bootloader is because you flashed custom recovery in a wrong way. I had a same problem too.

Try doing this: there is a guy which has a YouTube channel called ROMkart support. Pretty underrated. I think he's the only one making that kind of content on realme 6. I will provide you with this twrp version which i found on his telegram channel. This is the only one which is working for my realme so i don't know about you.I tried downloading twrp for realme 6 from official site and their application,but it never worked and i had a same issue you have. while i was booting in recovery it went to bootloader. I'll provide you with files but do it with your own risks. Im not responsible for damage it might do to your phone. Something that works for my phone doesn't mean it will work for you,but you can try. Backup stuff so if anything goes wrong you will still have data and stuff. Here are the steps to install custom recovery:

1.Download this twrp recovery img in your pc

2. run cmd in platform tools

3. Connect your phone to pc and enable usb debugging

4. Check if adb recognizes device by command: adb devices.

It will run a deamon and you should allow it on your phone.

5. Then rerun the command again, it should display some code and a word - device next to that code. That's when you know adb is functioning

If it says code and a word unauthorized,then it's not working so you should allow deamon to run on your phone too. It will open a dialogue in you phone once you type adb devices Commmand.

6.if it works,then type command : adb reboot bootloader.

This command will reboot your phone to bootloader, the one you said before(oplus verify fail thing).

7. Then check if fastboot is working by command:fastboot devices

8. If you type the command,run it and nothing happens then it means that fastboot drivers are not working properly. You can check on YouTube how to fix that. You just need to update drivers for android device in your pc

9. After you fix it when you type that command(fastboot devices) it should display some code again.

10.now you are sure it's working type command: fastboot flash recovery - and after recovery type space and then drag twrp folder on that cmd. It should display the directory of where you have twrp file.

11.it will flash a custom recovery on your phone. It will be done in few miliseconds.

12. After it's done , run command: fastboot reboot recovery.

13. It should open custom recovery now if it was flashed correctly or if it supports you device.

14.if twrp turns on, you might notice that it's alittle laggy. Idk why but that version of twrp is not working well. So ill provide second custom recovery pbrp which you need to flash from twrp.

15. Drag pbrp file into you phone and then go to custom recovery. Hit install and choose pbrp zip file. Before flashing choose recovery partition and wait for flashing. After it's flashed do not reboot to system. Go back to twrp l, reboot and reboot to recovery

16. This should reboot again in recovery but pbrp will be installed instead of twrp. And it will work much smoother.

The issues you might face are these: you might not be able to permanently flash custom recovery. You can check that by rebooting into system and then rebooting into recovery again after you finished installing. If it turns custom recovery then you are fine. If it doesn't that means vbmeta is in action so you need to disable vbmeta. I really don't remember how i did it but i tried it several times like 5-6 and bootlooped my phone several times becauso of that because i wasn't able to flash custom recovery permanently. If you have issue with it you can contact me and ill help you.

Another issue which you might have and i really don't have a fix for that is rom encryption. I had the same issue on stock firmware with android 11 and even on this arrowos custom rom with android 13.If your custom rom is encrypted, custom recovery might not show phone files or show them with random names. In that case you will not be able to flash pbrp from twrp before you don't have usb and otg or micro sdcard where you can transfer pbrp zip file to access it from twrp. The reason i think for that is because that custom recovery doesn't support the encryption which custom rom uses. Even if i set a password on my phone pbrp still doesn't ask for it and not even for the key, which is necessary to decrypt the system to access files normally. I've been researching about that recently but I cannot find if anyone knows the solution for that phone. There are no lot's of custom recoverys for this phone too so i cannot surely tell but i tried pbrp,twrp,orange fox and none of them worked and decrypted my system. Some custom recovery might work but I don't know for now.

The advice i can give you for now is to use decrypted custom rom if you want to be able to flash files without any issue.

I had evolution x custom rom which worked pretty fine but i didn't like it because of some bugs so i got rid of it. Now I can't find any good custom rom which is decrypted so idk.