You’re facing a firmware level check, maybe inherited from LineageOS.
To ensure it will run smoothly, an Android ROM must relies on firmware at compatible level.
So the installation script includes a firmware level check.
Older firmware may run your Android ROM without noticeable problems, but you’re highly recommended to install latest firmware or the whole MIUI.
Please see more technical details here : Redmi Note 7 Pro (violet), couldn't flash the ROM: Zip Treble compatibility error or directly https://gitlab.e.foundation/e/backlog/-/issues/476#note_27505
BTW latest stable firmware and MIUI for your device is V12.0.5.0.QFHINXM (https://xiaomifirmwareupdater.com/firmware/violet/ and https://xiaomifirmwareupdater.com/miui/violet/, India version).
Please avoid downloading firmware or ROM from random sources, they may include crap.