To anyone interested, I did call the Canada Revenue Agency about where to claim GitHub Sponsors income. The first agent did not know, so I got passed up the line to a more experienced agent, who also did not know but put me on hold to find out. They said to claim it on https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-return/completing-a-tax-return/personal-income/line-10400-other-employment-income.html. GitHub remits to me in CAD$ - I asked if I should do any conversions from USD$->CAD$ because GitHub is in the USA. The agent said there was no need, just claim the CAD$ amount I received. If I ever wanted to claim expenses against the income then that'd be a different thing, but they say this will work for my scenario.