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@koalalump said, this Weekly ROM version is excellent on Mi 9T / Redmi K20. I don't have any issue.
I tested the rom and the result was the same. Then tried the patch and... nothing.
Finally, I discovered that the rom has an error, the directory on which the patch installs the .bin file. contains a directory with the same name as the file so it can't install the file normally.
This is not a problem per se, but the partition is read only and can't remount it with write permissions, even from TWRP..
Also, from TWRP, the directory's content is completely different,
For now, I will install the latest stable rom, bur I wanted to report the problem here to advise other people, that could have the same problem.
Thanks anyway for your help.