Hi there, and welcome to the forum!
I have an early 2011 Macbook Pro, still running on High Sierra (MacOS 10.13) which doesn’t receive any more security updates.
I once managed to install Ubuntu 20.04-Lts on it with refind, but it somehow got destroyed in the process of setting up a non-extant rescue partition for the MacOS. Afterwards I didn’t want to go through the hastle all over again, as of yet.
Did you use refind, too, and do you stlll dual-boot with MacOS, or has it become a Linux-Only 'puter by now?!
Before I forget: Could this post potentially solve your issue?