Friend, making a detailed tutorial takes a lot of work, but I'll leave some references and tips for you.It seems so great
By any chance, is there a Tuto that explains step by step, with the requirements (software, drivers, etc..), how to do steps 2, 3 and 4 please?
2) Installing ROM with unlocked bootloader

[CLOSED] Convert your Moto x30 Pro (CN) to Edge 30 Ultra (EU)
FIRST OFF: If you have not bought the phone yet and plan on getting it: DON'T. The camera is broken and Motorola refuses to communicate with their customers. Is a fix coming? I someone working on it? Who knows. The phone is also still on Android...

Other references
https://kfhost.net/flashfile
https://mirrors.lolinet.com/firmware/motorola/oneli/official/
https://t.me/s/motoupdatestracker
3) Change the software channel
Just need to run this command “.\fastboot oem config carrier reteu”
IMPORTANT: Choose a channel that has OTA updates, like RETEU
Updated software channel list
ATTMX = AT&T Mexico
BELLCA = Bell Canada
MOVLA = Movistar Latin America
MSTLA = Movistar Latin America
MSTCL = Movistar Colombia
ORANGE = Orange (France?)
RETAPAC = Retail Asia-Pacific Region
RETASIA = Retail Asia
RETBR = Retail Brazil
RETEU = Retail Europe
RETCA = Retail Canada
RETIN = Retail India
RETLA = Retail Latin America
RETMX = Retail Mexico
RETUS = US Retail
RGRCA = Rogers Canada
TIMBR = Tim Brazil
TKPCA = Telus Canada
VZW/VERIZON = Verizon Wireless USA
4) how to lock bootloader
https://forum.xda-developers.com/t/guide-relock-bootloader-should-work-in-all-versions.4057497/
I hope it helps. Good luck.
Caution. Study all the videos and information well so as not to damage your smartphone.