Obviously, everyone has to check whether the broker is regulated or not, whether the broker supports your trading style or not etc.
But 2 additional important things I will point out here:
1.Never deposit a large amount of money to a broker account at first without going through a complete cycle. I mean first deposit a small amount which you are okay in loosing, then trade with small lots and then, withdraw the entire amount and monitor how fast and easily the entire process goes on from which you can get an overall idea of the broker's operation in back end. If they are hesitant in the withdrawal process or delays the process etc, then there must be some suspicion which you need to check again.
2.Watch each and every trade carefully you place manually or by EA to check whether there operate your account in A-Book or B-Book or do they have only B-Book that's how generally the market maker brokers operate. But 99% of brokers operate in both A-Book and B-Book and switching between them based on your initial deposit and trading performance.
So don't struggle to make money in a broker by any system if your account is in B-Book, there is no way you can make money in long run if your account is in B-Book using any EA or manual system and you will never know that as well until you closely observe the execution of each and every trade during entry and exit. So find a broker where you are sure that all your orders are directly sent to the liquidity providers.
Artificial General Intelligence