The /e/ documentation Install /e/ on a Samsung Galaxy S9+ - “star2lte” talks exclusively about TWRP-Recovery, but not about eRecovery, a fork of Lineage-Recovery’s own development.
The version of TWRP we used to test the ROM was 3.3.1-1
I used TWRP 3.5.0_9-0 from Decmber 2020 for the /e/OS ‘Q’ installation; in the meantime TWRP version 3.5.0_9-1 from Jan 27, 2021 is available.
However, after the successful and straightforward installation of /e/ OS ‘Q’, eRecovery e-0.13 and no longer TWRP Recovery is installed on the S9+ without any indication.
eRecovery is good for processing OTA updates and for a few simple additional tasks. However, the feature set is much smaller than that of TWRP Recovery.
The ‘Update recovery’ option in the developer options is functional. It allows the automatic update of eRecovery with system updates “Update the built-in recovery with system updates”.