Based on discussion on HN several days ago, I have started using Hashcards (markdown-based flash cards with FSRS; run from command line, but view cards in the browser). Once set up, it's pretty simple (e.g., no fiddly settings) which helps a lot. Getting new cards added is easy — especially with a Keyboard Maestro macro that I made (global keyboard shortcut pops up a window to enter Q/A and select a deck, i.e. md file, to append to; entering text only on the Q line creates a cloze-deletion card instead). Recommended.

My use case is drilling English --> target-language sentences, as well as law-related knowledge, miscellaneous facts, etc. Still mulling over what to do about other skills-based practices, à la Andy Matuschak's concept of "spaced everything".

- Hashcards: https://github.com/eudoxia0/hashcards

- HN discussion about Hashcards: https://hn.algolia.com/?q=hashcards

- Matuschak's "spaced everything": https://notes.andymatuschak.org/Spaced_everything