Quote from some old guide:

The Importance of Being Connectable:

When it comes to torrents, being connectable can go a long way in helping your ratio. Connectivity is directly related to port forwarding, your router, and incoming torrent connections. Here's how it works:

You upload a new torrent. After going through the upload page and adding the torrent to your client, the client connects to the tracker to do the following:

1. Tell the tracker it is going to begin seeding a torrent.
2. Ask the tracker if there are any peers it doesn't know about.

Normally, no one has downloaded the torrent from the site between the time that you upload the torrent and when you add it to your client. So your client will now wait, for 45 minutes (or however long it's been told to wait by the tracker), until it will connect back and ask for more peers.

Now suppose someone downloads your torrent from the site after you added the torrent to your client. Normally, the person's client will ask the tracker for peers, to which the tracker will return your IP address to connect to. That client will then connect to your client, using the IP address and port number it got from the tracker pertaining to your client and the port it accepts incoming connections on. This is where being connectable comes into play. We'll assume your IP address is 139.129.43.5 and your port number used for torrenting is 3058.

When the peer attempts to connect to you on that designated port, your router has to know what to do with the incoming connection. It receives an incoming connection from the peer, on port 3058. If you have your port forwarded to your client correctly, that is, you've told the router what to do with incoming data on a specific port, the router knows to send anything coming in on port 3058 to the computer your client is running on. Now, if you are not connectable, the router doesn't know what to do with items coming in on port 3058, so they are discarded, and the other peer isn't able to connect to you.

If your port isn't forwarded correctly, the peer who just added your torrent to their client will have to wait for 45 minutes, until your client updates with the tracker, and gets the new peer's IP address and port to connect to. If the peer is connectable, you will then make an outbound connection to them, and it will connect successfully. Outbound connections aren't normally blocked by a router, unlike incoming ones, this is why a client doesn't need a port forward for outgoing connections. This scenario is also why you can still seed even if you aren't connectable. This can have very negative consequences for your ratio though as I will now explain.

Here's how not being connectable will hurt you. When you are seeding a torrent in a large swarm and a new peer comes online, his client will attempt to make connections to the other peers. If you aren't connectable, you will have to wait (at max) 45 minutes until your client learns of their existence, before you can start uploading data to them. During this time the peer is getting data from other peers, but not you. By the time your client finally learns of the new peer's existence, the client will already be done downloading! You won't get nearly as much upload than if you were connectable. Depending on the size of the torrent, your client may not get any upload for that peer, because he will have completed the torrent before your client even knew he was present.

The absolute worst case scenario is when both peers aren't connectable. Neither peer will be able to connect to the other, and both will sit without connection indefinitely.

I think you should try to find a VPN that supports it, but you can live without it if you have to.

If you don't have a listening port other clients can't request a connection. You can still limp along without accepting incoming connection requests and it may not even make a big difference. Still it's a lot better to have it. You'll connect to more peers.

BTW, It's not always necessary to use port forwarding to enable a listening port, but commonly it is. Machines with a public facing IP don't need to use port forwarding, but most people are either on a private network or VPN where it's required.

I'm more concerned with the fact that they're removing features without reducing price or making up for it elsewhere. I have no desire to support that business when there are perfectly fine alternatives.

Is it really crucial to find a VPN that supports port forwarding

It's crucial when the only seeder won't open their port.

what’s the go to option now that it’s becoming increasingly uncommon

My opinion: I wish qbittorrent 4.6 would release sooner, it comes with I2P support, which I've seen discussed on lemmy a few times.

Is it really crucial to find a VPN that supports port forwarding?

It is not required but you will have a much better torrenting experience by being connectable (port forwarded). When you are fully connectable you are able to make direct connections to all peers in torrent swarms so overall your upload/download speeds would be faster and you can still participate in small torrent swarms.

When you are firewalled (not port forwarded) you can only make direct connections to peers that themselves are connectable (port forwarded).

In practice when you are in large torrent swarms it may not make much difference, there's often plenty of connectable peers in large torrent swarms that you can connect with. However in smaller torrent swarms if no one is connectable then all the firewalled peers can only see each other, no data will transfer. They are all stuck waiting for a connectable peer to join the swarm & help with the data transfer.

If you care about seeding you need it. If you don’t you’re fine but come on, you know you should care lol.

I use PIA, probably the cheapest option out there and it does have PF.

I notice the difference with it off. Its shit without it. I get no incoming connections to existing torrents I'm seeding and when I add a new magnet link it just stays stuck on obtaining metadata and never Downloads.

When I have the port forwarded it runs like clockwork.

My setup is containerized with a gluetun container acting as the VPN network and the interface binded inside the qbittorrent container. .

One important aspect is that two peers without port forwarding will never be able to connect to each other. This is important for torrents with low amount of peers. Unless a connectable peer comes in to essentially relay data by grabbing the content from the other person and then seeding to you, you won't be able to download. For popular torrents with plenty of connectable peers to go around this is less of an problem, it will only cause some performance issues.

No you don't need port forwarding

You may notice slower speeds and difficulties downloading rare stuff. Generally, you'll probably be OK if you're looking for well-seeded files.

See here for a bit better explanation.

Port forwarding lets you connect with a peer that doesn't have port forwarding basically. You may not notice a difference.

I think it just makes you more discoverable to other peers for dl/seeding, don’t quote me on that I might be misremembering

Aside from torrent the other p2p where an open port can be important is Soulseek, you could be blacklisted by users from downloading pretty quickly if you don't/can't share music.

I switched to mullvad a few months back and what I noticed coming from AirVPN is how much less captcha requests I get, I'm not much into p2p so I'll probably stay with them.

If you want to run a seedbox behind a VPN (like I do) then you'd want to be connectable, so a VPN with portforwarding would be crucial. I run my own OpenVPN server on a public VPS (so a dedicated IP instead of shared IP) but I only use private trackers so a dedicated IP is fine and also technically required, so my local seedbox whitebox server connects to my OpenVPN server as an OpenVPN client, and tunnels all traffic over the VPN with an iptables prerouting rule on my public VPS for the traffic on my qbtorrent-nox inbound port to reach my local server.

This way I can run whatever hardware I want in my seedbox and have full control over the hardware while also masking my home IP.

Port forwarding tripled my upload speed. I didn't really notice a difference on download.

Let me know if you want a year subscription to Speedify. It came bundled in a Humble Bundle ages ago and I have never used it since I have a lifetime subscription to Windscribe.