I am re-building all my templates based on debian-10-minimal. HiDPI scaling works with all programs (Xft.dpi in /etc/X11/Xresources/x11-common) except for JRE based programs.
In the past, if I installed gnome-settings-daemon and then set the scaling factor in gnome-tweaks it also worked with JRE based programs. That was with kicksecure (installed on top of debian-10-minimal by following Install Kicksecure ™ inside Debian) as well as a full debian-10 and fedora-?? (long ago) template.
Doing the same on a debian-10-minimal doesn't work: the gsd-xsettings daemon is running, but any configurations I make in gnome-tweaks have no effect. So my strategy is to see which additional packages kicksecure installs in the system. Unfortunately there are many. Anyone have an idea which of these I should try?
* debsums
* desktop-file-utils
* dialog
* dmeventd
* groff-base
* helper-scripts
* inotify-tools
* libaio1
* libasan5
* libatasmart4
* libatomic1
* libevdev2
* libevent-2.1-6
* libfile-fnmatch-perl
* libfstrm0
* libgudev-1.0-0
* libinotifytools0
* libinput-bin
* libinput10
* libirs161
* libisc1100
* libisccc161
* libisccfg163
* libitm1
* liblmdb0
* liblsan0
* liblvm2cmd2.03
* liblwres161
* liblxqt0
* liblzo2-2
* libmagic-mgc
* libmagic1
* libmpx2
* libmtdev1
* libnspr4
* libnss3
* libpci3
* libpcre2-16-0
* libpcre2-8-0
* libpipeline1
* libpkcs11-helper1
* libpolkit-agent-1-0
* libpolkit-gobject-1-0
* libprotobuf-c1
* libreadline5
* libsysfs2
* libtsan0
* libubsan1
* libuchardet0
* libudisks2-0
* libvolume-key1
* libxcb-icccm4
* libxcb-image0
* libxcb-keysyms1
* libxcb-randr0
* libxcb-render-util0
* libxcb-shape0
* libxcb-util0
* libxcb-xinerama0
* libxcb-xkb1
* libxkbcommon-x11-0
* linux-libc-dev
* lsb-release
* lsof
* lvm2
* menu
* most
* msgcollector
* usability-misc
There are more, but I don't think they are candidates:
* anon-apt-sources-list
* anon-icon-pack
* apparmor
* apparmor-profile-dist
* apparmor-utils
* apt-transport-tor
* bash-completion
* bc
* bind9-host
* binutils
* binutils-common
* binutils-x86-64-linux-gnu
* bootclockrandomization
* bubblewrap
* busybox
* damngpl
* bzip2
* dist-base-files
* distro-info-data
* dnsutils
* dosfstools
* dpkg-dev
* file
* fuse
* gcc
* gcc-8
* gdisk
* gnupg2
* hardened-malloc
* jitterentropy-rngd
* kicksecure-base-files
* kicksecure-cli
* kicksecure-dependencies-cli
* libbind9-161
* libbinutils
* libblockdev-crypto2
* libblockdev-fs2
* libblockdev-loop2
* libblockdev-part-err2
* libblockdev-part2
* libblockdev-swap2
* libblockdev-utils2
* libblockdev2
* libc-dev-bin
* libc6-dev
* libcc1-0
* libdevmapper-event1.02.1
* libdns1104
* libdouble-conversion1
* libdpkg-perl
* libfuse2
* libgcc-8-dev
* libgeoip1
* libgpgme11
* libkf5windowsystem-data
* libkf5windowsystem5
* libntfs-3g883
* libpam-systemd
* libparted-fs-resize0
* libparted2
* libpython3.7
* libqt5core5a
* libqt5dbus5
* libqt5designer5
* libqt5gui5
* libqt5help5
* libqt5network5
* libqt5printsupport5
* libqt5sql5
* libqt5test5
* libqt5widgets5
* libqt5x11extras5
* libqt5xdg3
* libqt5xdgiconloader3
* libqt5xml5
* libwacom-common
* libwacom2
* libyaml-0-2
* lxqt-sudo
* make
* man-db
* net-tools
* ntfs-3g
* open-link-confirmation
* openvpn
* parted
* patch
* pciutils
* policyrcd-script-zg2
* python3-apparmor
* python3-dateutil
* python3-distutils
* python3-gevent
* python3-greenlet
* python3-lib2to3
* python3-libapparmor
* python3-pyqt5
* python3-scapy
* python3-sdnotify
* python3-sip
* python3-socks
* python3-stem
* python3-yaml
* sdwdate
* secure-delete
* security-misc
* sysfsutils
* timesanitycheck
* tor
* udisks2
* wget
* whonix-initializer
* whonix-repository
* xz-utils
* zsh
* zsh-common