For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Application:ERP:GNUHealth:Factory/openSUSE_Tumbleweed/Application:ERP:GNUHealth:Factory.repo
zypper refresh
zypper install trytond_account_invoice_stock
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Application:ERP:GNUHealth:Factory/15.6/Application:ERP:GNUHealth:Factory.repo
zypper refresh
zypper install trytond_account_invoice_stock
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Application:ERP:GNUHealth:Factory/15.5/Application:ERP:GNUHealth:Factory.repo
zypper refresh
zypper install trytond_account_invoice_stock
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Application:ERP:GNUHealth:Factory/15.4/Application:ERP:GNUHealth:Factory.repo
zypper refresh
zypper install trytond_account_invoice_stock