Hello!
Which brokers provide great margin trading services & have wide range of stocks marginable?
Thank you! 
Hello!
Brokers that have competitive margin rates and likely have more stock inventories are:
- Interactive Brokers - https://brokerchooser.com/broker-reviews/interactive-brokers-review
- TradeZero - https://brokerchooser.com/broker-reviews/tradezero-review
If you have any further questions, please let me know.
Best regards,
Chris