You can run (something like) /opt/plesk/php/7.4/bin/php /usr/lib64/plesk-9.0/composer.phar --1 to downgrade to v1.x
Look in the schedules task list for composer and schedule the above command after the one from plesk to keep it on v1.
@IgorG i downgrade by running:
# /opt/plesk/php/7.2/bin/php /usr/lib64/plesk-9.0/composer.phar self-update --rollback
And then updated to the latest 1.x release using :
# /opt/plesk/php/7.2/bin/php /usr/lib64/plesk-9.0/composer.phar self-update --1
(I think this is beter than manually...