The temporary public policy allowing visitors who are holders of a valid visitor visa to apply for work permit within Canada has been extended until August 31, 2021. As long as there is a valid job offer for an employer-specific work permit, a visitor can apply inside Canada.
For more information please read here:
https://www.canada.ca/en/immigration-refugees-citizenship/corporate/publications-manuals/operational-bulletins-manuals/updates/2021-pp-exempting-visitors.html