Indeed :
- R is for “Red Velvet Cake” the original codename of the android system version 11
- S is for “Snow Cone” the original codename of the android system version 12
- T is for “Tiramisu” the original codename of the android system version 13
The easy installer is expected to install stable builds but, as i understood from actualities thread, not yet T builds…
Option :
- Downgrade to A11 to install latest /e/-R-stable.
- Stay to A12 and Install outdated and not maintened anymore /e/-S-dev nomore updates to wait.
- Upgrade to A13 to install latest /e/-T-dev.
From my point of view the last one is the best choice.
IMPORTANT ! : This /e/OS v1.18 includes the Android security patches available until November
So choose an older OnePlus Stock Firmware !