You have a good point with your first question profile="timestamp-update"] would also be updated when the room becomes vacant.
And to your second question, just trying to learn more about OH3 and keep finding that there are more elegant ways of solving problems and wanted to check before bashing out yet-another-rule.
That is a moving target and implies repeated re-evaluation (else it says 10 mins forever).
So it’s more complicated than first appears.
Doing calculations at the UI is one approach - so you’d need to identify what UI you want this to happen in.
The only option I would see, when not using rules is to play with the visabillity= option in the sitemaps file. Take a look at the Worx binding by Nibi79 and how he used 4 different lines to get an elegant solution
And to your second question, just trying to learn more about OH3 and keep finding that there are more elegant ways of solving problems and wanted to check before bashing out yet-another-rule.
I can’t speak to HABPanel but it’s pretty flexible so I bet you can calculate with date times in a widget for this.
In Sitemaps you are pretty much limited to the approach outlined by Richard, using visibility.
In MainUI Pages you have access to expressions and a date time library that you should be able to use to populate the text of a widget (see rossko57’s links). However, as rossko57 points out, the “X mins ago” will only be calculated when the page is first loaded. You’ll have to reload the page to force a recalculation of X.