Android 7+ and at least 500 Mb - 5 GB on storage, is official requirements from their wiki https://wiki.termux.com/wiki/FAQ#What_are_system_requirements
Personally I recommend also:
* 1.5 GB in storage is minimum for good perfomance, do not continue, if you have small storage, because it cause "no enough space" error
* arm64 proccessor and 64-bit OS, because on S1S13AF7 smartphone (Redmi 6A) have perfomance issues with 32 bit system, but maybe if install PostmarketOS on this smartphone it will be better because is more native Linux system than java wrapped Termux... Maybe also MIUI firmware issues
Anyway if you have low-end device, in step 1 when copying oneliner skip part with 'pkg update && pkg upgrade', but no any warranty, it can broke bot without upgrade Termux bootstrap packages. Also if your speed downloading updates very slow, press Ctrl+C, and try run `termux-change-repo` and select other region.