I’m not sure it’s related, on 7.1.4 I had a similar problem. Using ./seahub.sh start-fastcgi I was able to get a more verbose output why seahub failed to start and was able to troubleshoot from there.
For the forum thread, see here: Ubuntu Upgrade to 20.04 broke Seahub (ARM)
Maybe it’s something related for you or helps you find the correct direction to troubleshoot your problem