If you are speaking about Android, do you mean that you use a dedicated Android apk from PIA, or do you achieve these high speeds on Android kodi with the vpn addon installed in kodi?
Assuming you are using an app from PIA to establish your connection on Android, than this app could choose ipsec or pptp protocol, which is mostly faster (either because decryption is way faster, cause weaker, than openvpn, or because PIA has more bandwidth on ipsec and pptp than on their openvpn servers).
But LibreELEC is limited to OpenVPN, which is more secure, but mostly slower, especially on ARM systems, compared to x86/x64. And some VPN providers may share less bandwidth for the OpenVPN protocol servers, as these need more processing power, hence more energy consumption, less efficient for them and less users care whether it is openvpn or pptp, so they may calculate with this less demand and focus on high bandwidth for the other protocols.
It's just a guess, but this could be an explanation why your android and libreelec show so different speeds.