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I ended up using a transformation instead. Seems the EBNF notation doesn't support wildcarding

transformations: [args => {
                    if (args.type === "aws:ecs/TaskDefinition:ContainerDefinition") {
                        return {
                            props: args.props,
                            opts: pulumi.mergeOptions(args.opts, {
                                ignoreChanges: ['image']
                            })
                        };
                    }

                    return undefined;
                }],

Great solution!