Linuxcnc 2.9.4 and Mesa 7i97T

My current version is 3.4.9

But will it make any sense at all to try to configure the setup as long as I get an “unsupported board”

A little about the background for the project.
I have over time -as a side business - made several retrofits of older (woodworking)cnc machines
Normally I change the driveline to new hybrid steppers controlled by a plc with a control sw developed by ourselves (or in a few projects Mach 3&4), but in this project I have a huge 7ton Homag with very powerful Rexroth motors and drives where i have modified the drives to analog control.
Therefore I went for a LinuxCNC and a mesa 7i97T.
I accept there is a learning curve but it has been far more complex than expected.

I’m surprised about how many YouTubes are found about “LinuxCNC as easy as Mach3” a statement I have hard to believe unless you have 20 years of Linux behind you

You don't need "20 years of Linux behind you", get rid of that way of thinking. All you need to be able to do is follow instructions, minding syntax and not taking shortcuts, and be able to relay any error messages without leaving anything out. It is also to follow any links in replies, it saves those that reply having to repeat any info.

Oh and mesa wouldn't sell you a product that is deemed to work with Linuxcnc that doesn't .

Did you look at the download PCW attached, I think it was a simple config to get you going.

Upgrading mesaflash from the GitHub page may help with your issue .