I was able to install some applications using the following commands:
flatpak remote-list
flatpak remote-delete winepak
flatpak remote-delete --user winepak
flatpak remote-add --no-gpg-verify --if-not-exists winepak https://dl.winepak.org/repo/winepak.flatpakrepo
sudo flatpak install winepak tld.domain.Application
and for to know which apps are available for download, the following command:
flatpak remote-ls winepak