Hello Affinity,
first message here :-)
I already bought Affinity Designer (for Windows) and are now testing the photo beta version (1.5.0.39). I deleted the shortcut of photoshop to forces me to use affinity instead.. We will see^^ I am experiencing the same problem with the font.
I have a laptop with a 4k resolution (windows 10 64). If I use my laptop only I have no issue, the fonts are sharp.
However, I usually work with two attached monitors with a "classical resolution" of 1920X1080.
In that configuration, the UI fonts are indeed ugly.
I updated my drivers, played around with the refresh rate and resolution but couldn't fix it.
Thank you!
Tl;dr UI fonts are ugly with external monitor(s) on laptop