The default guide for Huginn installation works pretty well. The only part where you do get stuck is
sudo bundle exec rake production:export
So what really happens is that the console looks like it stuck, which is quite frustrating. Lets say you force quit this (Crtl^C). Try running it again and you will get an error like.
root@localhost:/home/huginn/huginn# sudo bundle exec rake production:export --trace ** Invoke production:export (first_time) ** Invoke production:check (first_time) ** Execute production:check ** Execute production:export ** Execute production:stop Stopping huginn ... rake aborted! 'sv stop huginn-web-1' exited with a non-zero return value: warning: huginn-web-1: unable to open supervise/ok: file does not exist /home/huginn/huginn/lib/tasks/production.rake:85:in `run' /home/huginn/huginn/lib/tasks/production.rake:77:in `block (2 levels) in run_sv' /home/huginn/huginn/lib/tasks/production.rake:93:in `call' /home/huginn/huginn/lib/tasks/production.rake:93:in `with_retries' /home/huginn/huginn/lib/tasks/production.rake:76:in `block in run_sv' /home/huginn/huginn/lib/tasks/production.rake:75:in `each' /home/huginn/huginn/lib/tasks/production.rake:75:in `run_sv'
So a bit of searching will lead you to this bug report, which actually is pretty confusing. Turns out the issue is with runit.
The solution provided by somm15 for ubuntu 18.04 works as well for Ubuntu 20.04 as well.
sudo apt-get install runit-systemd runit-helper
sudo systemctl enable runit
sudo systemctl status runit
Now you can rerun the init script exporting and you can continue with the installation guide!