Is there any plan to replace Mir?
An oft asked question has arisen on the Telegram channel once again and I thought I'd post an answer here for posterity:
Is there any plan to replace Mir? Since it's completely abandoned, it may take too much effort to maintain it, and it may better to switch to Wayland, if it's possible, since it has way more support. - so manpower could be used somewhere else (PWA maybe?)
"I can understand perfectly how the report of my illness got about, I have even heard on good authority that I was dead. [A cousin] was ill in London two or three weeks ago, but is well now. The report of my illness great out of his illness,. The report of my death was an exaggeration." - Mark Twain
Like the reports of Mark Twain's death, Mir's abandonment is based on a misconception.
There's a lot of confusion about this because "the internet" has confused toolkits supporting the mirclient API with servers using the Mir libraries. These are two different stories.
The mirclient API
The mirclient API is a way for application toolkits (and other client-side libraries) to use Mir. This API is abandoned: it is no longer under development and the Mir developers have deprecated it and will remove it "someday". I think UBports is the only remaining project to use it (the Mir support in Kodi, SDL2, gtk3, etc has been dropped).
UBports do need to switch from using the mirclient API to using Wayland before "someday" becomes "today". That is a multi-step process described here: The Way to Wayland (for Unity8)
The Mir server libraries
Mir was the core of Canonical's effort to enable "Convergence". [See: https://forums.ubports.com/post/18392 for my take on "Convergence"]. These libraries are still supported and developed by Canonical and there are a number of projects using them or planning to use them. Canonical has IoT projects, some experimental "desktop" work (including with MATE).
There is no reason for UBports to switch from using the Mir server libraries, they are the foundation on which Unity8 (and some other, less visible, components) are built. Even with the issues presented by the switch to using Wayland for applications the support for "Convergence" is unique to Mir and core to UBports.