NEVER give up!
Can you confirm its actually Chinese variant (eg box info, not phone settings)... Appears some Indian K20 Pro variants physically lack NFC hardware, and have been sold unlocked w/ global ROMs etc.
NFC cannot apparently be made to work on these Indian models, but Chinese variant has NFC and reportedly also works with later (10.3.12.0 MIUI onward) global or custom XiaomiEU ROMs.
https://forum.xda-developers.com/t/solved-no-nfc-on-redmi-k20-pro.3945229/
You should NOT need the mods you found on XiaomiEU site.
You DON'T need TWRP.
You likely DON'T need recovery.img DESPITE (factory) ramdisk (in boot) = no (because it's Xiaomi):
https://forum.xda-developers.com/t/magisk-general-support-discussion.3432382/post-84603817
Once you have 10.3.12.0 MIUI global or later installed, and ADB Fastboot PC drivers working, also extract boot.img from ROM package, then simply install Magisk APK, open app, click install Magisk, then NEXT (in Options with Recovery Mode UNCHECKED), click Select and Patch a File, select your boot.img, click Let's Go, wait for All Done!, boot to fastboot and flash patchedboot.img (as for ramdisk= yes). Boot to system. If it bootloops (system is corrupted message), simply flash UNPATCHED boot.img. You will likely need Magisk in recovery in this case.
If system boots, check you have root in Magisk app. If not, you will also likely need to flash UNPATCHED boot.img and Install Magisk in recovery.
If you have root (most likely), turn on Magisk hide in settings, reboot and run Check SafetyNet in Magisk app. If you get basicIntegrity pass but ctsProfile fail, install Universal SafetyNet Fix (and Busybox for Android NDK) Magisk module, reboot and check SafetyNet again. If you have pass, open PlayStore settings and check PlayProtect says Device is Certified. If not, clear Google PlayStore data and Google Play Services cache, reboot and check again.
If you have PlayProtect certified device, Install Gpay (if necessary), open Magisk app and toggle on Google Pay in MagiskHide list, then reboot. Next, clear Data for Google Pay, then open it and try setting up card(s) / NFC payment.
Nb. It seems that there is no longer a need to install SQLite fix for Gpay.
All best! PW