Hey there,
I have the same laptop as you and am thinking about upgrading to big sur. This is how I found opencore and olaria. It really looks promising! I'll definitely give it a try once I find some more time. At the moment I'm on Catalina with Clover. However, the graphics are not running smoothly and I can't figure out the issue. Everything was fine on Mojave, thanks to rehabman's repo. @YouHelp: would you be so kind to share your EFI from Catalina, if you still have it somewhere. Otherwise I'm excited to hear about the progress with getting big sur running on the u430.
Thanks!