A Neonatox package teaches, it doesn't just install.

#%NHO-0.5
# Package Maintainer: cargabsj175 

# Name:       transmission
# Version:    4.1.1
# Release:    n2026
# License:    GPL-2.0-or-later
# Repository: extra
# Arch:       i686 x86_64
# Splitpackage: base gtk qt

# BuildDep:   curl nodejs libevent gtkmm4 qt6-svg cmake...
# Dep(base):  curl nodejs libevent
# Dep(gtk):   gtk4 hicolor-icon-theme
# Dep(qt):    qt6-core qt6-svg

nbuild() {
  cd src/transmission-4.1.1
  cmake -B build -DCMAKE_BUILD_TYPE=Release \
    -DENABLE_GTK=ON -DENABLE_QT=ON -DENABLE_CLI=OFF
  cmake --build build -j$(nproc/2)
}

ninstall() {
  cmake --install build --prefix=$DESTDIR/usr
}

ninstall_gtk() {
  install -Dm755 build/transmission-gtk $DESTDIR/usr/bin/transmission-gtk
}

ninstall_qt() {
  install -Dm755 build/transmission-qt $DESTDIR/usr/bin/transmission-qt
}