I use multiple spaced repetition apps per day just for fun because I like doing flashcards as a hobby. I have tried this out, its good, but still not as good as the newest version of Supermemo. You can tell if you put the same or similar material into two or more apps. FSRS is much better than almost everything else out right now though and I think it will be better than Supermemo very soon. I tried Mochi Cards for about a year and it was just okay, a little better than a default Anki install. Mnemosyne is the same. The Supermemo SaaS app is okay, but I don't like how they structure their language materials.
For language vocab, I use Clozemaster, but then I put the sentence into Supermemo after I get it right because the SM algo is that much better. They also have ChatGPT explanations for each word of the sentence. I also put those into Supermeno.
Also, I have not found a flashcard program that lets you make cards as fast as Supermemo. With Supermemo, you paste in a chunk of text (ctrl-n), highlight a word you want to make cloze deletion from, and press alt-x. You can do it multiple times on the same piece of text, and every time you do it, you get a new cloze deletion card in your reviews. Almost every other app, you have to make a single card at a time. I think its because most other apps stick too hard to the cards and decks metaphor. Supermemo uses a tree structure to organize everything. It makes a big difference. Technically, you don't really need to organize anything though. People act like the material they learn is going to be categorized into neat decks in their head.
For language vocab, I use Clozemaster, but then I put the sentence into Supermemo after I get it right because the SM algo is that much better. They also have ChatGPT explanations for each word of the sentence. I also put those into Supermeno.
The hardest part is making good cards for sure. This will help with more ideas: http://arxiv.org/abs/2401.01257 and https://rust-book.cs.brown.edu
Also, I have not found a flashcard program that lets you make cards as fast as Supermemo. With Supermemo, you paste in a chunk of text (ctrl-n), highlight a word you want to make cloze deletion from, and press alt-x. You can do it multiple times on the same piece of text, and every time you do it, you get a new cloze deletion card in your reviews. Almost every other app, you have to make a single card at a time. I think its because most other apps stick too hard to the cards and decks metaphor. Supermemo uses a tree structure to organize everything. It makes a big difference. Technically, you don't really need to organize anything though. People act like the material they learn is going to be categorized into neat decks in their head.