I am evaluating Linstore and I have a few questions
First of all - do I need an HA controller at all? Without it does all my storage stop working when the controller node goes down? I am running proxmox on 3 nodes, all with storage
Then, if I do, can I do the NFS proxmox-gateway with this HA controller because the docs say it must NOT be setup like this, but I already did it because it was the last step for a ‘production’ deployment in the other doc I was following 
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First of all - do I need an HA controller at all? Without it does all my storage stop working when the controller node goes down? I am running proxmox on 3 nodes, all with storage
No, you do not need an HA controller. If the controller goes down, you will not be able to create, remove, or otherwise manage your storage, but existing storage will continue to operate as expected.
Then, if I do, can I do the NFS proxmox-gateway with this HA controller because the docs say it must NOT 1 be setup like this, but I already did it because it was the last step for a ‘production’ deployment in the other doc I was following 1  .
I believe what Ryan was saying in that blog is that his steps assume you have not configured an HA controller, not that the reader should not. Since you have already done this, you should create a LINSTOR Client configuration on each of the nodes listing each node as a potential controller. Multiple LINSTOR controllers are configured by specify them all in a comma-separated list. The LINSTOR client will try them in the order listed.