Do you have the required fonts? If so, are you able to reproduce this in vanilla? If not, this should be forwarded to JGRennison/OpenTTD-patches.

This may be related, I'm redirected from JGRennison/OpenTTD-patches#188.

Version of OpenTTD

nightly (openttd-20200902-master-g53a3d940b1)

Expected result

Font face and alias settings are effect rendering text.

Screenshot of OpenTTD 1.10.3:

Actual result

Font face and alias settings seem te be ignored while rendering text.

Screenshot of OpenTTD nightly (openttd-20200902-master-g53a3d940b1):

Steps to reproduce

Set the following font values:

small_font = SF Pro Text Medium
medium_font = SF Pro Text Medium
large_font = SF Pro Text Medium
mono_font = SF Mono Medium
small_size = 12
medium_size = 13
large_size = 18
mono_size = 12
small_aa = true
medium_aa = true
large_aa = true
mono_aa = true

Full openttd.cfg file.

@standaniels : good news, this recently has been fixed! Thank you for the report :)

@ecolortest : we haven't heard back from you. I am going to assume it is because you didn't have custom fonts loaded. If I am wrong, and after following the configuration snippet @standaniels gave it is still not working, feel free to re-open this ticket!

Thank you both!

Same with Russian, and I have not idea how to run it in English instead system language
OpenTTD 1.10.3

With 1.10.3 you need to set fonts in openttd.cfg (you can also change language there if needed). But please also try 1.11.0-beta1, it should use fallback fonts provided by OS (at least on windows).