In the last Q&A Dalton gave a list of devices that will be supported with UT based on Ubuntu 20.04. Unsurprisingly, the BQ4.5 isn't in that list.
To me the support for the BQ4.5 has always been a bit of a roller coaster. It was sold and supported by Caniconal, then dropped. UBPorts took over, but they weren't able to give proper support to the legacy devices. Eventually they were able to give proper support, but even when the upgrade to 16.04 happened, it was already clear that an upgrade to 18.04 or 20.04 may mean the device wouldn't be supported any more.
I think the development team has done a great job giving us a supported and well working 7 year old device. I for one thank them for that.
But now that this support will most probably end, the question is; What now? On the one hand I want to keep using UT because I really like it. On the other hand, I don't want my phone to be left in a drawer somewhere collecting dust, so what else can we run on it after the update to 20.04 happens?
I looked around a bit, but I don't really see options honestly.
We can keep using UT based on 16.04, but that means no more updates. Eventually it wont be (easily) possible to install apps (unless maybe the click-packages will be kept available somewhere online and we can download and install from there), and it may not be (easily) possible to install UT back to the device (unless the images and instructions are kept available somewhere).
I also looked around for other OS'es I know about, but none of them seem to have a port for the BQ4.5.
I looked for the following, but don't see ports for Lineageos (Besides, I'm unsure how well this would work on an Ubuntu edition device since it doesn't have the Android buttons), PostmarketOS, SailfishOS, LuneOS, Manjaro and Mobian
That doesn't leave much options of course. Maybe someone has other OS'es or ports they know of that can run on the BQ4.5? What are you planning to do once support ends?
 See Q&A 115 at 34:22. The list is
- Pixel 3a
- Volla Phone
- Volla Phone X
- Anything else people come in to do