For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ecsos:with_gnutls_3.7/openSUSE_Tumbleweed/home:ecsos:with_gnutls_3.7.repo
zypper refresh
zypper install filezilla
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ecsos:with_gnutls_3.7/15.4/home:ecsos:with_gnutls_3.7.repo
zypper refresh
zypper install filezilla
For 15.3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ecsos:with_gnutls_3.7/15.3/home:ecsos:with_gnutls_3.7.repo
zypper refresh
zypper install filezilla