ARB fails to run with MacPorts Installation

[Channy-736 (Chantel)]

I've installed the latest version of ARB (6.0.2) through Macports (2.6.4) with Xcode (12.5) on macOS Big Sur 11.3.1. I also have xquartz installed. When I try to run arb by typing in the terminal the command:

arb

I get the following error:

/opt/local/bin/arb: line 94: ARBHOME: unbound variable

Next, I manually set the path to the location of the arb Unix Executable file, located in /opt/local/bin/arb using the following lines of code:

ARBHOME=/opt/local/bin/arb;export ARBHOME
PATH=/opt/local/bin/arb:$PATH
export PATH

but then once I try running arb again, I get an error different from the user's in this issue: ​https://trac.macports.org/ticket/47262 (I don't get the Can't open display: :0 error):

chantel@MacBook-Pro-2 ~ % arb
Ignoring set ARBHOME '/opt/local/bin/arb' (overridden by explicit call of '/opt/local/bin/arb')
Using ARBHOME='/opt/local/bin/arb'
/opt/local/bin/arb: line 55: Fusion.app/Contents/Public:/opt/X11/bin:/Library/Apple/usr/bin:/Library/Frameworks/Mono.framework/Versions/Current/Commands: No such file or directory
Using properties from /Users/chantel/.arb_prop
Directory /Users/chantel/.arb_prop not found - creating ...
Directory /Users/chantel/.arb_pts not found - creating ...
Directory /Users/chantel.arb_prop/macros not found - creating ...
Directory /opt/local/bin/arb/lib/macros not found - creating ...
mkdir: /opt/local/bin/arb/lib: Not a directory
Please wait while the program ARB is starting .....
Waiting for '/Users/chantel/.arb_tmp/sockets/arb_launcher.62500'..
[arb_launcher[0]: Starting 'arb_ntree'..]
**Fatal ERROR: Environment Variable ARBHOME not found !!!**
   Please set 'ARBHOME' to the installation path of ARB
ARB: Loading 'ntree.arb'
Environment variable 'ARBHOME' should contain the path of an existing directory.
(current content '/opt/local/bin/arb' has been ignored.)
**Fatal ERROR: Environment Variable ARBHOME not found !!!**
   Please set 'ARBHOME' to the installation path of ARB
Environment variable 'ARBHOME' should contain the path of an existing directory.
(current content '/opt/local/bin/arb' has been ignored.)
[arb_launcher[0]: 'arb_ntree' has terminated with error 1]
[arb_launcher[0]: All launched processes terminated]

Session log has been stored in /Users/chantelbiegler/.arb_prop/logs/session.20210510_211933.62509.tgz
    and is also accessible via /Users/chantelbiegler/ARB_last_session.tgz

ARB terminated abnormally

The run log has the following output:

[arb_launcher[0]: Starting 'arb_ntree'..]
Fatal ERROR: Environment Variable ARBHOME not found !!!
   Please set 'ARBHOME' to the installation path of ARB
ARB: Loading 'ntree.arb'
Environment variable 'ARBHOME' should contain the path of an existing directory.
(current content '/opt/local/bin/arb' has been ignored.)
Fatal ERROR: Environment Variable ARBHOME not found !!!
   Please set 'ARBHOME' to the installation path of ARB
Environment variable 'ARBHOME' should contain the path of an existing directory.
(current content '/opt/local/bin/arb' has been ignored.)
[arb_launcher[0]: 'arb_ntree' has terminated with error 1]
[arb_launcher[0]: All launched processes terminated]

TL;DR - Clearly, there is something wrong with ARBHOME, based on the fatal error that says the environmental variable ARBHOME isn't found. I just have no idea how to fix that.

My apologies if this is a noob question - I'm brand new to ARB and I've found the installation process to be archaically difficult, but maybe that's just me. I have searched the forums, but I haven't found anything else I can try for this issue.

Thank you so much, I would really appreciate it if I could get this working!!