I'm creating a custom mega menu design in odoo15. Try to add a group that template shown a error, 

i.e, 

ValueError: Invalid field 'groups_id' on model 'theme.ir.ui.view'

Same time, removed that groups in a custom template, error not came while upgrading the theme, but access rights issues came after edit and select the mega menu in website...

In backend, manually give the access rights , error not shown while click the mega menu.