TimeManager is dead, long live the Temporal Controller!
TimeManager turns 10 this year. The code base has made the transition from QGIS 1.x to 2.x and now 3.x and it would be wrong to say that it doesn’t show ;-)
Now, it looks like the days of TimeManager are numbered. Four days ago, Nyall Dawson has added native temporal support for vector layers to QGIS. This is part of a larger effort of adding time support for rasters, meshes, and now also vectors.
The new Temporal Controller panel looks similar to TimeManager. Layers are configured through the new Temporal tab in Layer Properties. The temporal dimension can be used in expressions to create fancy time-dependent styles:
TimeManager Geolife demo converted to Temporal Controller (click for full resolution)
Obviously, this feature is brand new and will require polishing. Known issues listed by Nyall include limitations of supported time fields (only fields with datetime type are supported right now, strings cannot be used) and worse performance than TimeManager since features are filtered in QGIS rather than in the backend.
If you want to give the new Temporal Controller a try, you need to install the current development version, e.g. qgis-dev in OSGeo4W.
Update from May 16:
Many of the limitations above have already been addressed.
Last night, Nyall has recorded a one hour tutorial on this new feature, enjoy:
Free and Open Source GIS Ramblings 
Bravo Mr. Dawson!
Temporal Controller might have nice abilities in dealing with vector data. However, its support for raster files seems very rudimentary so far. According to https://github.com/qgis/QGIS/issues/36251 they might think about how to deal with a temporal dimension in NetCDF files, but so far, this is no alternative for TimeManager.
It is really a pity that you already stopped the development! It was a great plugin but after installing Ubuntu 20.04 and QGIS 3.14 I have some issues with dependencies now.
Unfortunately, changes to timestamp datatype handling in QGIS 3.14 broke TimeManager and I don’t have resources to fix something that will soon be obsolete. However, if someone else wants to take over and maintain TimeManager until all features are migrated to Temporal Controller, I’d be glad to hand over.
It seems that I will still be using using your plugin until Time Controller will support pre-100 AD dates (which I doubt will ever happen; It’s kind of shame that this pretty major issue is swept under the rug (not only in QGIS) when such a big portion of GIS users are from fields that deal with large time scales.)
Here’s hoping that the compatibility won’t break in future versions.
Anyways, thanks for the great work!
The Temporal Controller is great, and Nyall’s video helped me take advantage of the expressions to build a more dynamic visualisation. But thank you for giving us Time Manager for so long. It really was one of my favourite plugins in QGIS!