...
Custom connectors in PowerApps only work with Swagger version 2 definitions.
To get the JSON from the swagger, remove
/swagger/ui/index
& add/swagger/docs/v1
to the end of the URLMTAPI JSON: https://wwwappstestext.tc.gc.ca/Saf-Sec-Sur/13/MTAPI-INT/swagger/docs/v1SIAPI JSON: https://wwwappstestext.tc.gc.ca/Corp-Serv-Gen/5/SIAPI-ISAPI/swagger/v1/swagger.json