Comment 1 for bug 1875947

In archlinux there is a patch for grsync to use gtk3. I used following steps to make binary package that's just works for me:

1. Download package from mirror to home directory: https://www.archlinux.org/packages/community/x86_64/grsync/

2. Open up terminal make a new deb:
mkdir archpkg
tar xf grsync-1.2.6-4-x86_64.pkg.tar.xz -C archpkg/
apt download grsync
mkdir edit
dpkg-deb -R grsync_1.2.6-2_amd64.deb edit/
rm edit/DEBIAN/md5sums
rm -r edit/usr/
mv archpkg/usr/ edit/
fakeroot dpkg-deb -b edit/ grsync.deb

3. Install new package with:
sudo dpkg -i grsync.deb