I had trouble installing termux after initially attempting to install it from the Google Play store.
I uninstalled termux itself, but there was another termux app (termux-something?) that I also had to uninstall in order to be able to install the latest from F-Droid.
What I would try is to install Split APKs Installer and then install Termux APK with it. If installation fails, there is a more verbose log than you would get with default installer.
“INSTALL_FAILED_SHARED_USER_INCOMPATIBLE: Reconciliation failed…: Reconcile failed: Package com.termux has no signatures that match those in shared user com.termux; ignoring!”
and
“app has requested an already existing shared user but their signatures do not match.”
note:
after i was not able to install the f-droid version, as a test, i was able to install and use termux from google play.
i did uninstall the google version before trying to use SAI