Submit the same paper to several journals/conferences
No. Simultaneous submission is rarely considered acceptable.

Each journal or conference will have a simultaneous submission policy (a.k.a. dual submission policy) that you can look up. Make sure you read it and, if you can’t find it, ask. With a handful of exceptions (e.g., law reviews), they all prohibit simultaneous submission. If you ignore this policy, it is considered academic misconduct and could get you in trouble. And the chance of getting caught is very high.

I understand your frustration with the duration and uncertainty of the review process. However, if everyone started doing simultaneous submissions, the system would get even more clogged up. The bottleneck is a shortage of reviewer time and simultaneous submissions only consume more reviewer time. Simultaneous submission is viewed as a means of cheating the system that is unfair to those who follow the proper policy.