Trying to update to Linuxcnc 2.9

I've been running linuxcnc 2.8.4something under Mint 20. The ideal solution would be Mint 20 or 21 and linuxcnc 2.9. As far as I can tell, this is not an option due to Python 3.10 on Mint.

I have a spare SSD, so I installed Debian 12 and linuxcnc-uspace. I'm using parallel ports, my short term jitter more than doubled (vs. Mint 20/2.8). Not good.
I have been trying to switch to the RTAI kernel, have not been able to figure it out.

Advice will be greatly appreciated,
Steve

I just did the last one:
Package linuxcnc is not available...

So I'm not accessing the right set of files.

When I try to install linuxcnc_2.9.2_amd64.deb I get an error.
trying to overwrite '/usr/share/applications/linuxcnc-documentation.desktop', which is also in package linuxcnc-doc-en 1:2.9.2

I removed linuxcnc-documentation.desktop and still get the same error.

If you are using the ISO on the downloads page, it had a bug in it and it was installing an old version of linuxcnc which could cause issues
I built a fixed ISO but not sure if Andy deployed it. 
Then an issue arose with the ethercat security keys for their repository
I just finished building  a new ISO  but the ethercat is not fixed. Feel free to give it a go from my Google Drive if you are not going to use ethercat
drive.google.com/file/d/1gEQzgHsj_LjHiGB...k1Z/view?usp=sharing

I decided to stay with 2.8. I don't really need better jitter, maybe I should spend my time on woodworking instead of software! Thanks, thread bookmarked for future reference.