WordCamp Łódź 2019 (Workshops on theming in Sage 9):
WordUp Trójmiasto 2019 (The Twelve Factor WordPress App):
WordUp Poznań (Sage 9 in practice)
WordUp Kraków 2018 (Sage 9 in practice)
WordUp Trójmiasto 2018 (Sage 9 introduction and ACF workflow):
You can get slides from this prelection.