Learn English – What does ‘I would be up for it?’ mean

It means 'whether or not this is of any use/value'.

For what it's worth, I'm very sorry I broke the window.

means, for example, that it may not make any difference to the physical state of the window, but that hopefully the apology helps placate you.

It's almost a kind of self-deprecation; it's saying 'No words of mine will be adequate, but...'

It can mean "I'm single" or "I'm not in a relationship."

It can also mean "I don't have any plans" - when used in conjunction with a date or time, or that you can be contacted at that point in time.