Openflights has long been the tool many of us use to log their flights, but it has two big problems:

1 - You can't add new airlines, so my recent flights on ITA Airways and Breeze, for example, can't be logged as such.
2 - The "List flights" function currently appears to be broken. It lists flights only partially.

It hasn't been maintained for years, either, and that is a concern. It might stop working one day and take all our logs with it.

Flight Memory or Myflightradar24 are imperfect replacements; they do not offer the same functions. The former is also antiquated and not maintained, and the latter, for example, does not let you input the actual distance flown.

So, does anybody have a good alternative that isn't one of the above sites? Thank you!

You manually input the actual flight miles? Or does Openflights import that for you?

I didn't realize this was a metric people tracked.

1/ I think you can, airlines, airports - I checked their FAQ/help not long ago because of this and there's a way to do it (https://openflights.org/help/airline)
2/ my flights seem to list correctly

Please refer to the following thread:

Yes, you can input them manually. OpenFlights gives a a default number if you do nothing, but obviously actual distance flown differs. So I go to Flightaware to find that number, and enter it manually.

I'm now curious where OpenFlights gets that default number. It doesn't appear to align with gcmap.com figures.

Of course, gcmap is going to be lower than actual flight miles, because it's the shortest route, not actual.

Does Flightaware provide info for each flight, say, if it deviates from course it will be longer than usual?

No airline provides credit for, or informs passengers of, "actual" miles flown, to include flight path changes, "go arounds", etc. They each use a standard (for that carrier) distance calculated point-to-point between two given airports.