fluentd-ui start command gives error - bundler: failed to load command: rackup

Hi Team,
I am getting below error after executing "fluentd-ui start" command.

$ fluentd-ui start
bundler: failed to load command: rackup (/home/avi/.rbenv/versions/3.3.0/bin/rackup)
/home/avi/.rbenv/versions/3.3.0/lib/ruby/gems/3.3.0/gems/activesupport-5.2.8.1/lib/active_support/core_ext/module/delegation.rb:156:in `delegate': Delegation needs a target. Supply an options hash with a :to key as the last argument (e.g. delegate :hello, to: :greeter). (ArgumentError)

raise ArgumentError, "Delegation needs a target. Supply an options hash with a :to key as the last argument (e.g. delegate :hello, to: :greeter)."

I have below configuration in my setup
=========================================
01) OS details
OS: Ubuntu 23.10
# ufw status
Status: inactive
# sestatus
SELinux status: disabled

02) Ruby installation-
I installed ruby using below sequential commands-

sudo apt update
sudo apt install git curl autoconf bison build-essential libssl-dev libyaml-dev libreadline6-dev zlib1g-dev libncurses5-dev libffi-dev libgdbm6 libgdbm-dev libdb-dev
curl -fsSL https://github.com/rbenv/rbenv-installer/raw/HEAD/bin/rbenv-installer | bash
rbenv install 3.3.0
rbenv global 3.3.0
export PATH=$HOME/.rbenv/versions/3.3.0/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin

ruby -v
ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-linux]

cd $HOME/.rbenv/versions/3.3.0/bin
gem update builder
gem update --system

03) fluentd-ui Installation -
gem install -V fluentd-ui
fluentd-ui setup

04) start fluentd-ui
fluentd-ui start
At this command I am getting above mentioned error.

05) Troubleshooting efforts -
a> Tried by uninstalling and re-installing fluentd-ui
gem uninstall fluentd-ui
gem install fluentd-ui
b> Tried installation using above steps 01 to 04 on ubuntu 20.04,22.04,23.10
But the faced the same error.

I have never worked in Ruby development hence not able to fix the issue.
Kindly help.
[fluentd-ui start error.txt](https://github.com/fluent/fluentd-ui/files/14305795/fluentd-ui.start.error.txt)