Manual doesn't mean terminal. They offer config files you can just add to Network Manager. They offer both WireGuard and OpenVPN options, and I've done that (with a different VPN provider) on Bazzite without issue. It's really easy.

As for that reddit comment, you need to do your due diligence and verify the claim. I don't know what your threat model is, and only you can decide if you think it looks legit. I've inspected it in the past, and it seemed legit to me, but I wouldn't recommend it to anyone without the disclaimer that they need to look for themselves. You are implicitly trusting the VPN operator to do what they say (e.g. no logs, etc.).

Adding a mysterious middleman (that may just be trying to do something nice and legit for the community) introduces an untrusted agent into the mix. So take a look and weigh if you think it seems deserving of your trust.