Different scale on apps (one display)

I’m still getting used to Ubuntu (20.04) on my Lenovo ThinkPad Carbon X1 after being a Mac user for 10 years.

When setting up, I found the resolution made things far too tiny and I’m sure I changed a few things, including the scale slider (first) and then I dropped my resolution (from 3840×2160 to 1920×1080). The resolution change made everything look ok, except Telegram, which I think is still being scaled and looks really large.

But now I can’t find the scale slider any more and can’t find how to make it look ‘normal’…

Thanks in advance for any advice.