I'd recommend against it. Flarum is still in beta, and isn't recommended to be run in production as there's no guarantee it'll work.
And, last time I attempted to do this, it indeed did not work due to incompatible dependencies, and database errors. In fact, i don't believe I've ever managed to run flarum successfully.
It also, is no longer actively developed based on the github repo.
Flarum looks the part, but the code powering it is not stable. I'd suggest you find a different forum software.
The original author/owner of the project left the team in June 2019. Ever since the Flarum team has been pushing hard towards stable, where stable relates to the extension API not stability at all. Activity cannot be measured from the repository flarum/flarum by the way, because that's simply (an extremely stable) skeleton. Everything happens mostly in https://github.com/flarum/core.
Flarum isn't installable on top of Laravel. I'm not even sure this will happen at all with the speed Laravel keeps pushing out versions. Flarum has focussed on LTS Laravel versions as much as possible, even so an update to the latest 6.x LTS is still on the todo. An integration is possible though, the easiest perhaps is by using passport and the Flarum passport extension.
@luceos I have an question about this old post: i also have the intention to run flarum being part of a domain (no subdomain). Do you have any advice how to set this up? Thanks in advance.