Phones bought from /e/ with /e/OS installed are usually running stable builds (rather than dev builds). Rooted debugging is not available on `stable’ builds, which means that there is in any case no effective ‘easy’ way of backing up your user-installed apps and app data.
The easy way on dev builds is to use Android Backup and Restore Tools project, but that needs either a rooted phone or rooted debugging.
I also believe that stable builds ship with /e/'s recovery rather than TWRP, and /e/‘s recovery does not provide the backup functionality that TWRP does. TWRP backup is the only working backup solution fir devices with `stable’ builds, and is only available if it is possible to install TWRP as the recovery on your device. SOrry, but I don’t know whether that is the case.
It’s worth reading this thread for more details of how to backup using TWRP