Hi et bonjour @Manuekris. There’s one thing I’d like to draw your attention to, on your research for a small phone: About 2 years ago there was a big shift taking in the shape of mobile phones - the screen ratios from devices changed from 16:9 to 18:9 (or even up to 19,5:9). That means screens became higher an slimmer. Like this, manufacturer were able to “squeeze” larges screens in existing phone form factors.
That means a 5" phone from 2017 has about the same size as 5,8" phone from 2018/9.
I agree that it becomes more and more difficult to find non-huge phones, but there are still some rather powerful smaller phones - as for instance the Samsung S9 (5,8"), which is supported by /e/.
Anyway, good luck finding the perfect phone for yourself.