Was the camera set to take pictures in HDR mode already? It’d be weird enough that turning this off doesn’t make a difference.
Perhaps your settings are out of place for some strange reason. Try to open the camera settings and at the bottom choose “Settings Manager > Reset settings”. This will set all camera settings back to the defaults. As you will see there, you can also save your current settings to a file and restore from it later, in case you’re concerned with losing your current setup.
I also have the FP3 with /e/ pre-installed so we should have the same version of everything. If you upload that file I’m happy to try it out on my phone and see if maybe I can spot the issue. For reference you can find the backup file using the Files app under Android/data/foundation.e.camera/files/backups.
If you are not comfortable sharing that information, review some of the settings that may consume processing power but that you may not actually need, as @Anonyme said.
Camera > Settings > More camera controls: Pause after taking photo
Camera > Settings > Photo settings: Image quality
Camera > Settings > Photo settings: Image format
Camera > Settings > Photo settings: RAW
Camera > Settings > Photo settings: Noise reduction original images
You shouldn’t need to lower the camera resolution, but image format can be an important factor. For most use cases JPEG is enough (the default quality at 90% is also fine), but disable RAW if you don’t intend to edit pictures with Photoshop. For noise reduction mode, don’t save original images either.