We'd been using a cloud notes app for three years to store research for a government-funded study. Forty researchers, thousands of notes, links, tags, and attachments. Then the company announced the service would shut down in ninety days.
We switched to Portable Notes over a weekend. The data was exported as a folder of Markdown files. Some notes had embedded images that needed manual relocation. Some links pointed at the old service's URLs. It took about a day to clean up.
Three years of research, recovered from a directory of plain text files. The project was back on track before the next funding review.
One thing we learned: plain text outlives apps. It outlives companies. If your data matters to you, store it in a format that doesn't care what software you use to read it.