Operating system: Debian 10
Graphics card: n/a
Broken: Local git build: 2.81, a571ff2c16c6, master 2019-08-09
NLA Editor: Select-all, ][ bracket selection, etc. will highlight strips, and those can be, for example, moved around. However, they must be manually mouse-clicked, for them to be actually selected for Tabbing into editing their actions/curves. If this is intended operation, I do not see an indicator to distinguish between what the strips are selected for. (See 'More info' below).
Exact steps for others to reproduce the error
Make multiple strips. Select with a, or [, ], etc. (just don't select with mouse). Tabbing into edit mode will not work except on manually-mouse-selected strips. Select any strips with mouse and those will be editable when tabbing in to edit them.
From what I can tell there is a separate selection for manually (mouse) selected strips. I don't see an option to convert the selection into a tab-editable selection of strips (do we have that?), nor any visual indicator to differentiate the type of selection the strip belongs to.