Lubuntu/Linux mint dual boot gets stuck booting

I have been running Linux mint (version 19.3) on a Thinkpad X1 Carbon gen 7 for a while. I recently installed Lubuntu (version 20.04) on a separate partition. I do not have Windows on this computer. Since installing Lubuntu, about half the time when I reboot my computer or turn it on, it gets stuck on the boot screen. Based on the timing, I assume when I installed Lubuntu it messed up my boot loader somehow. I have been holding the power button to turn it off and trying again, and it usually boots just fine then, but I worry this will damage my computer in the long term.

I haven’t been able to find any support for problems booting a computer after adding a second linux operating system in the absence of Windows, and all of the support for computers stuck booting seems to be for getting the computer to turn on at all, rather than preventing it as a recurring problem.

I ran bootinfoscript, but I’m not sure which data from the output are relevant to include here. I’m happy to share some/all of the output, whatever’s helpful.