Hello,


Is anyone have experience to solve limitations of the L4 license for the routerbord?

The HEX have L4 license that mean the limit of 200 L2TP sessions per device. https://wiki.mikrotik.com/wiki/Manual:License

Do the limit above applicable for the routerboards? Can I upgrade the license from L4 to L5/L6?

Yes, the license limit is applicable to RouterBOARDs.
So you will not be able to do more than 200 tunnels on a RouterBOARD with an L4 license.

You can buy an L5 license, and apply it to the RB.
There is no upgrade (you can't just pay the difference) in RouterOS licensing, so you need a new L5 license, and the previous L4 license will be lost.