I've used it until about a year ago. In theory it's pretty good, but it never reached critical mass. Sites were not using it, because it didn't pay off and users weren't using it because you didn't have enough sites. Most things I used it for was blogs, quite a few of the ones I had in my RSS reader have/had flattr, and I supported them that way

Years ago when I tried to use it, the default currency was the Euro. As an American, doing the currency exchange on their website added friction to the transaction.

Flattr was midly popular, then Patreon ate their cake.

Not really a fan of both, as pretty much any hobby project that tried to monetize with Patreon lost its soul. If something is free and suddenly they want money for it, even if there are free alternatives that usually doesn't work. To each their own, some probably like it. I avoid reoccurring monthly costs, where possible and prefer one time costs or just good old advertisement.

I cannot agree with the idea that something wanting to pay the bills has "lost its soul".

For sure. I know a lot of Twitch streamers, and that is a full-time goddamn job. Wanting to be able to pay rent off of something that a lot of people like (and some of the streamers I know are north of 10,000 viewers when they're on, so while they're not huge they're not small either) is not a big ask. Yeah, there are alternatives--but if you like what you're watching and you're not hurting for cash, throw a buck a month in the hat.

I find Patreon funded content to be far less soulless than advertising funded content. (This comment brought to you by Audible).

I believe that's a risk and some projects have probably not managed it well. For what it's worth, I've been happy with the half-dozen or so projects I support on Patreon, so it's certainly not a universal failing. I think it's important for the creators to phrase it as supporting a work that is already free, rather than as charging for providing a service.

I like the idea of micropayments to support content.

But I wasn't able to get Flattr to accept my credit card. Wasn't sure if it was because they are Sweden-based and I am in the US, as I didn't keep trying.

I agree, I think this is a possible next maturation of content creation. People don't like advertisements, it is difficult to generally monetize online content otherwise from my understanding.

It reminds me of a similar theme in the music industry, record labels make most money, artists make little.

Whoever can solve this problem for the masses of content creators is surely bound to make lots of money.