What conlangs are you learning (about)?

I will say that a huge advantage Esperanto has going for it is the number of speakers. Online, you can find many communities. Once you're in the community, you can literally couch surf the world, staying with fellow Esperantists. There's a huge corpus of reading material (I have a physical edition of The Hobbit in Esperanto), and even a few movies. It pops up here and there in popular culture, too; the name of the watch company Movado was actually taken from Esperanto.

Being popular means having chances to use the language. Not just study, and play by yourself, but interact with other people. I lurk in Ido and Lojban chat rooms, and they're mostly dead; Esperanto chat groups tend to be active.

The biggest thing, for me, is when a conlang is used for something other than just discussing the conlang itself. Esperanto has that going for it, and so it's always the conlang I return to. No, it's not perfect. Yes, it has some internal politics and debate, most lately especially around gender issues. But it has a certain momentum, and if you're looking for something you can use, Esperanto is the best choice (IMHO).

Edit 2023-07-02 I forgot to mention! There's an entire Mastodon instance dedicated to Esperanto; you're expected to post in Esperanto: https://Esperanto mast on host.

Obviously, a better choice would be a living language. Chinese or Hindi give you the most bang for your buck. But if you like traveling to Germany, learn German.

Heck, learning Latin is a fantastic use of time! It gives you a foot in the door to a half-dozen popular languages - enough to literally make yourself understood in a pinch.

For the internet, and if your interest is conlangs, I'd support your pick of Esperanto. Languages have the most value when there are other people to talk to with them, and Esperanto is the conlang with the most speakers, in the world, by far. Plus, it's a nice language, and will teach you a lot about languages in general. I think it's a great teaching aid for parts of speech and language construction; it's simple and straightforward.

One last caveat: Esperanto is notoriously Western influenced, and is reportedly harder for Asian native speakers. I don't believe a truly neutral language is possible, although Lojban is close: it's equally hard for everyone, regardless of native tongue. (That's a friendly dig at you Lojban folks, just a small joke).

Edit because it's a nicely done book, some eye-candy:

I've been checking Esperanto now and then occasionally. Never got deep into it. Each conlang has its purpose, and Esperanto is a fascinating reflection of the era it was born from.

I speak some bits of Esperanto. Simple sentences, really; "mi nomiĝas [enmetu nomon]" tier. I could've progressed further on it if I wasn't prone to the "oooh shiny" syndrome, and Sanskrit didn't take so much of my time back then.

I also can read and write Tengwar, but I don't know any conlang using it, not even Sindarin. (I use it mostly with Italian and Portuguese)

Beyond that I'm trying to learn the basics of my own conlangs Tarune and Meznagar as I'm making them. Specially the later as it has a bit more of a normal phonology, the former has stuff like pre/post-nasalised stops and uvulars that give me a hard time.

It's been ages since I actually worked on any, but way back I got reasonably deep into Lojban

Another conlang I've been interested in for a long time is Toki Pona, and because it seems so easy to learn, I might start learning it too. The community for toki pona seems especially welcoming and wholesome, so that's a plus too!

I think Duolingo has esperanto.