Made in LibreOffice Calc
If you want to be OS-agnostic, try https://www.libreoffice.org/discover/calc/ also happens to be free which is nice :)
It doesn't download stuff automatically from your bank/broker, but imho that's a plus. The security risks are just not worth the benefits.
LibreOffice Calc is a great open-source, free spreadsheet alternative to Excel. That's mostly what I use now.
Ledger is great if you want to keep really detailed accounts and generate really detailed reports. You can do anything with it and your data is all simple plaintext, so you can easily port anything to it and port the data from it to anything. The documentation is important to read, has a lot of good info.
In the end though, the most important thing for me was realizing that tracking every single transaction and everything down to the dollar was a waste of my time. What I needed was the big picture, the overall budget split between saving/investing, expenses, debt, and spending; progress toward long-term goals, etc. Find whatever helps you most easily see the big picture, and clearly see how you can 'move the needle', with the least work. If you need the detailed itemized bits, find something that does that easily, but consider whether maybe you don't.
> Documents I created with the "Secure spreadsheets" extension are in a format that's very hard to read as a human, and can't be opened with Gnumeric or LO Calc (I will be able to get the data out, but it's going to be a hassle).
Can you elaborate a bit more on how you created the documents and how you exported the data? If you used the option to export the sheets as .xlsx files, what kinds of issues did you run into?