Starting from 8.5.0 the ext-gd extension is required, so when running composer install, it verifies if the extension is present on the agent and fails when it can't find it.
A temporary fix is to make composer ignore platform requirements with
composer install --prefer-dist --no-interaction --ignore-platform-reqs, but in a long run we probably need GD on the agent.
Starting from 8.5.0 the ext-gd extension is required, so when running
composer install, it verifies if the extension is present on the agent and fails when it can't find it. A temporary fix is to make composer ignore platform requirements withcomposer install --prefer-dist --no-interaction --ignore-platform-reqs, but in a long run we probably need GD on the agent.