Here is a list of channel sellers: https://supertestnet.github.io/list-of-channel-sellers/

I am particularly excited about liquiditystr, which is a frontend that lets you explore liquidity ads created by users of some FOSS LSP software. 4 people are currently running that software and advertising channel sales, with the cheapest option being a channel with 1 million sats of inbound capacity (about $1000) for a cost of under 900 sats (less than $1).

> 2. What are the major concerns/factors that affect who you open a channel with?

- Cost of the channel

- Duration of service

- Reliable uptime

- Good connections

- Success of payments

- Privacy policy

> 3. Are there any privacy considerations?

Yes. Your channel counterparty gets to see some data about transactions that you are involved in, if they pass through his or her node. He or she gets to see partial amount info, partial fee info, timing info, payment hashes that might be linkable to you, and he or she gets to see that your node is the next hop on the route or, if you are the sender, they get to see that you are the prior hop on the route.

Ideally, your LSP should have a nondisclosure policy, a habit of regularly deleting this data, and no means of contacting them, that way nothing can be subpoena'd from them. If an LSP does not seem to publish a privacy policy but DOES have a way to contact them, consider asking them to publish a privacy policy and to disable their contact form.

> 4. Is 21K enough to do anything?

I'm not sure what you mean by "anything." If you mean "is there anything I can buy for 21k sats?" then yes, that's worth about $20 so you can buy a gift card with it from bitrefill, for example. It's also plenty for the kind of lightning work I do, which is mostly experimental. But if you're a heavy lightning user and spend your coins often, you'll probably run out of outbound capacity pretty fast and have to frequently top up your lightning wallet, which could be annoying. In that case, I would get a bigger channel of at least 200k sats.

> My goal is just to open a small channel to start testing BOLT12 payouts from @OCEAN

It seems to me that a channel with 21k sats of inbound capacity would be fine for such tests.