Hi @Decafgreentea welcome to the /e/ forum. I think you are wise to think ahead. This post Xiaomi, Downgrade MIUI V12.0.5.0 and ARP (anti roll back protection) talks of my experience of #anti-rollback. I think that you will find it hard to get back to Android 10 with an official ROM. The easiest thing will be to wait for or hope for an /e/ Android 11 build. (Others might know what the time frame might be.)
The https://forum.xda-developers.com/ would be the place to find clues about downgrading the device and then installing an official Android 10 ROM, please do not expect it to be easy without some Xiaomi experience ! 
Check also UnOfficial Builds - /e/ community for an Android 11 build.