YaST2 is a QT application. To adjust its font sizes, try qt5ct, or edit font= in ~/.config/Trolltech.conf directly.
# zypper info fetchmsttfonts
Loading repository data...
Reading installed packages...
Information for package fetchmsttfonts:
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Repository : OSS
Name : fetchmsttfonts
Version : 12.0-bp154.1.19
Arch : noarch
Vendor : openSUSE
Installed Size : 22.6 KiB
Installed : No
Status : not installed
Source package : fetchmsttfonts-12.0-bp154.1.19.src
Upstream URL : https://corefonts.sourceforge.net/
Summary : Helper package to download Microsoft Core fonts for the Web
Description :
This package contains a helper script that downloads and installs
a number of TrueType fonts collectively known as corefonts, or the
Core fonts for the Web. Originally made available my Micosoft under
a non-free End-user licence agreement (EULA), they continue to be
distributed subject to the same licence terms. The user is shown
a copy of the licence text upon execution.
The Core fonts for the Web include: Arial, Arial Black, Andale Mono,
Monotype, Courier New, Comic Sans MS, Georgia, Impact, Times New
Roman, Trebuchet MS, Verdana, Webdings.
Except for the version, fetchmsttfonts is the same in 15.3.