Here is a guide on popular hosts, that I have had a good experience with, and that I recommend.
Heroku is an option that I personally use to host some of my apps for free.
DigitalOcean is a very reliable service with viable security. I personally use it for my major projects (2PG, DBots, codea.live etc.). It costs money, but hosts apps 24/7, without extra challenges. As of writing this, I have not experienced any notable downtime, even with >2 years of service.
There are many hosting services, however I will only recommend the ones I have had a great experience with, and I hope you will too.