I should’ve clarified a bit more. So, I use a hardware keyboard (Logitech) and the Amharic keyboard setting is ‘automatic — Amharic‘. And for Gboard, I only use it with my phone (Google Pixel) because the Android version offers way more languages, keyboard options, etc (which are strangely unavailable in iOS).
The hardware keyboard doesn’t seem to have any long-press or shift + options for diacritics. I can use, for example, SHIFT + S to make ፅ rather than ጽ or use SHIFT + … to make any other consonant-vowel syllable combination, but no luck with diacritics.
I’ve attached an image of how it works on Gboard for Android (by long-pressing the ፤ key) to give a better idea of what I mean and the difference from the iOS & hardware design;

[Edited by Moderator]