Hey Brian,
the Raspberry Pi 3B that is inside the stock Onefinity Controller already has a 64-bit-capable CPU. The outdated Raspberry Pi OS from 2017 that runs on the Onefinity <=1.2.xx SD card images is an image of the 32-bit architecture “armhf” (ARM hard float), but switching to the 64-bit architecture “arm64” will work out of the box since the Raspberry Pi 3B is in fact made for it.
You can check this by taking an empty SD card and writing the most recent Raspberry Pi OS (64-bit) to it and boot it on the Raspberry Pi 3B.
As Onefinity states:
This has a major rebuild that is 64 bit which will work with either RPI3 or RPI4.
So no need for an upgrade path, you will be able to simply install 2.x firmware with a 64-bit OS image when it left beta status on your old Onefinity Controller.
PS: OT: Don’t you know how to use the quote function of this forum? It’s really simple:
Off-topic: I notice that you do not use the quote function of the discourse.org forum software, what has the disadvantage that there is no attribution in the texts you quote. That is just the advantage of the discourse forum software: The automatic attribution! To use it, you have already noticed that when you select a piece of text from another posting, a little box appears that you can click on:
Try it out! By using the quote function, not only you get the correct attribution inserted automatically, but the complete posting is available hidden through the little icon on the top right of the quotation!