Just because something has a price associated with it, that does not make the pricing model inherently correct or just. The majority of research papers, at least in the U.S., are (or historically have been, I don't know the data now under the current administration) publicly funded, one way or another. Publicly-funded research should not be behind paywalls.
Have you tried Flickwars? I don't own it, but played a demo version at a board game convention maybe five years back. I still keep wanting to pull the trigger on buying it but I've been trying to reel in my boardgame-purchasing problem a bit.
Most flicking/dexterity games are pretty abstract: lightly themed, if they're themed at all. And a lot of the ones that are themed, somehow don't get it "right". Flickwars is pretty cool in that it's got a light space battle theme with asymmetric team powers. It also has a neoprene board which, while not being as satisfying as polished wood, makes a surprisingly satisfying flicking surface. There's a modular setup to the game, where players place obstacles on or (because of the neoprene surface) UNDER the board. This meshes nicely with the space theme as you can consider these obstacles as gravitational anomalies. All-in-all, it's a pretty lightweight game, but it's a fun diversion from heavier board games.
Almost twenty years ago, I brought a crokinole board into my work and it became a very popular diversion. We came up with a cutthroat version where four players could play individually rather than the more traditional 2v2 four-player variant.
Generally, crokinole is a much less punishing game than carrom, if we're talking about Indian carrom boards. American carrom boards, that were really popular in after-school programs when I was growing up, have relatively HUGE pockets than the Indian boards, in addition to being smaller boards. American carrom is like playing 8-ball, Indian carrom is like playing snooker.
I like carrom a lot, but I'm terrible at it. I'm at least a reasonable player at crokinole, and it's a lot easier to introduce others to the game without them getting too frustrated by it.
Often in tabletop crokinole play, the "sand" isn't even used. Modern boards are often slick enough to get away with playing without it, and if it's a board that you roll out regularly, you may not want the cleanup overhead associated with using shuffleboard "sand."
Also note that you'd never use actual sand on a crokinole board or tabletop shuffleboard. Sand, wax, or powder is what the shuffleboard products are referred to as and are made of specially formulated silicone beads (much less abrasive than, say, beach sand) or cornmeal, or even sometimes ground walnut shells.
I prefer Mango Languages, which I get for free through my public library. The progression feels better to me, it's not as gamified (sorry for using that word), and there is some (though not a ton of) actual lesson content in there. For example, learning Spanish, it gives some context on the different usages of "Ser" vs. "Estar" for "to be", and it includes discussion on gendered nouns. DuoLingo may have gotten to some brief lesson content at some point, but for me it was too grating to continue with and I quit before I made much progress with it.
> The Author is arguing for replacing the chain with power wires, by generating power from pedaling and feeding it into the motor (with efficiency losses of 5%)
My understanding is that the efficiency loss is strictly limited to delivering electrical power back to mechanical power via motor instead of via the chain drive. The problem with this design is that it completely eliminates the ability to deliver mechanical energy directly. The rider pedaling charges the battery which then powers the motor. Going from mechanical energy to stored electrical energy is going to introduce a much greater loss in efficiency than a mere 5%. In a more standard e-bike model, when the rider pedals, my understanding is that they are delivering mechanical energy directly, bypassing the conversion to electrical energy. I may be wrong as I am not very familiar with e-bikes, but, if this is the case, the 5% figure seems highly misleading.
The "Handy Library" Android app includes an ISBN scanner and allows you to import and export collection data.
You could also check out some of the tooling and APIs around openlibrary.org. Unfortunately, I think it's basically a moribund project, but may have sufficient tools for your needs. I know they have a list feature, but I don't think ingestion is particularly easy; nor am I sure of the import/export functionality around their lists.
edit: I'd forgotten about librarything (mentioned in another comment). They have better tooling that openlibrary.