Ahh.. you don't have an xgs1250. That image just isn't a good fit for your actual device it seems.
You should put up as much info, photos etc as you can here:
https://svanheule.net/switches
The DTS for your device would need to be worked out.
It seems like it might be close to the Hasivo S600WP that is being discussed here
To set expectations, OpenWRT will almost certainly not work 'well' with your device right now.
If you just want a switch that works, best to stay with the stock firmware.
If you want to get involved in the development and testing of OpenWRT for this switch, then you probably want to get a development environment setup to build the OpenWRT images.
Ollivers gitlab repo has a branch realtek-wip that has lots of progress towards these switches, and there's a few other github etc repos that have bits and pieces also.
We're still working on getting the DTSes correct, and finding tweaks to the drivers required for various PHY/SDS configurations.