As a BC resident, you are considered to reside there and your Self-Employment would be based there as well. Only if you had a permanent business establishment elsewhere, would you choose a province other than BC as your province of Self-Employment. If you were self-employed in 2017, enter the province or territory where you had a permanent business establishment.
https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-re...