This may be subjective as I'm on a FullHD (1920x1080) laptop screen, but I noticed that the Web Installer font size is a bit too small to read. To be more specific, v18.11.16 is the last version where the body font-size property is set to 14px in bootstrap.min.css. From v19.05.00 onwards the size decreased to 12px and this makes the textual elements (including the button labels) appear a bit too small, and are harder to read compared to previous Koha versions. Please view the attached screenshots for a side-by-size comparison. I think this may be related to Bug 22023. Possibly relevant excerpt from commit a344b8cf8c: "The modified default CSS resets the base font size in Bootstrap to better match our global CSS. A side-effect of this is that toolbar buttons ended up looking smaller than they should. Changing the button class solves this."
Created attachment 105022 [details] Koha v18.11.16 - body font-size set to 14px
Created attachment 105023 [details] Koha v19.05.00 - body font-size set to 12px