Bricked phone and without operating system. What can I do?

[Kaiman]

Hello, I have a problem, let me tell you:
I have been trying to install the Pixel Experience ROM on my Redmi 8A, I installed TWRP and downloaded the ROM, however (after deleting the partitions) when trying to install the ROM I got error 255, so I was looking for the cause may have been my version of TWRP, so I decided to reinstall it.

So, I rebooted the phone and went into Fastboot mode and changed the TWRP version, however here comes the problem, I can no longer access the TWRP and got stuck in the Fastboot screen, is this happening because the phone no longer has an operating system? If so, is there anything I can do?

 

[ciubex]

Is your phone response in Fastboot:
- if you connect it to a PC, is your phone correctly identified into the Device Manager (Windows only)?
- what is displayed on CMD (Command Prompt terminal) if you type below command:

fastboot devices

If your phone is responding to fastboot commands, then you can flash back a stock rom to your phone.
Make sure that you really have a Redmi 8A (olivelite) device to not brick your phone harder!

Firmware page list: https://xiaomifirmwareupdater.com/archive/miui/olivelite/ (look for archives with extension .tgz, use 7Zip to extract the archive content)
Official Miui Flash tool: https://new.c.mi.com/global/miuidownload/detail/guide/1 (The tool is available on Fastboot Update section)