Load balancing across multiple providers - gateway or server?

Question

Computer networks

good afternoon, dear, I want to put 3 Internet providers into the network at the same time.
I am tormented by the question, should I organize it all on Debian or buy a good gateway?
For example, in the characteristics of the Zyxel ZyWALL USG 300 it says "Load balancing between several providers", I think this is what I need, but alas, the sellers could not advise me whether it would suit me or not. Can anyone recommend a good gateway with such capabilities? What would the gateway balance users from the 1st provider to the 2nd, depending on the load. Ie that at the same time some users would use the first Internet, and the second users the second Internet?
Alas, I did not find articles that were understandable for myself, on setting up this task on Debian, etc. If anyone has interesting links to articles on this topic, please share.
I found an interesting topic, on which I will try to implement this idea on a micro-table.
Mikrotik. Failover. Load Balancing

Answer 1

The other day I solved a similar problem on Mikrotik, which I advise you. There is enough information, the piece of iron is extremely flexible.