By another bizarre coincidence, I planned to start doing and recording pomodoros in 2020.
(For proof here’s the blog post from yesterday where I mention it though it’s mostly about other things. Also I realize now I published this post after yours but I just checked lesswrong.)
Google Keep has this feature if you don’t want to use a whole app for this feature. On any note you can click the bell to make it notify you at a set time and on a set schedule.
(I really like Keep as a note taking app but haven’t tried Apple notes, evernote or others so I didn’t recommend it at the top level)