You can try installing epson-inkjet-printer-escpr driver from AUR which does contain drivers for ET-2850
You can enable AUR in software center from Preferences → Third Parties, but remember that AUR packages are not official, provided by users as-is. You may want to see: [Need-To-Know] About Manjaro and AUR
I would also recommend enabling avahi-daemon service (for discovering printers) if you are trying to install the printer via network and not via cable.
After that you should be able to normally (via system setting GUI / CUPS) add a printer (at least I was able to install my EPSON printer) - I’m on KDE Variant. But remember to choose correct driver which should now be available.
Optionally you can configure the printer directly in cups by visiting http://localhost:631/admin (you login with your system credentials)