Thank you so much for your answer, Jonas.

One of the collaborators is working in the same studio.
A physical board with "Todo," "Doing," and "Done" sounds like a great idea.
I didn't come up with the possibility as I'm a heavily digital-oriented person. I will give it a try.

For another person, the one who showed a kinda panicked reaction to Notion - she suggested me to use Slack together on the other day. It was quite surprising for me. She said that she found it useful when she communicates with her business partner with slack.
It was a great suggestion from her. While I can record and share the overview of the tasks without forcing her to install new tools.