Ok I found on this forum the following suggestion to make the change to resume=UUID permanent
To make the change permanent, edit /etc/kernel/cmdline and rebuild your initramfs: sudo reinstall-kernels
So I did that, did a system update, rebooted, and it booted fine.
Not sure how /etc/kernel/cmdline resume=UUID value got corrupted in the first place but, if you have the same problem at least this is a fix.
For the googlers looking for this solution: EndeavourOS won’t boot, running start job for UUID that does not exist.