system storage full 521GB what is it how do I clear it?

Freeing up disk space - Time Machine snapshots

Applications -> Utilities -> Terminal

tmutil listlocalsnapshots /
    Snapshots for volume group containing disk /:
    com.apple.TimeMachine.2021-04-01-142742.local
    com.apple.TimeMachine.2021-04-01-163342.local
    com.apple.TimeMachine.2021-04-01-174425.local
    com.apple.TimeMachine.2021-04-01-192243.local
    com.apple.TimeMachine.2021-04-01-203820.local
    com.apple.TimeMachine.2021-04-01-222814.local
    com.apple.TimeMachine.2021-04-01-232930.local
    com.apple.TimeMachine.2021-04-02-002823.local
    com.apple.TimeMachine.2021-04-02-012748.local

tmutil deletelocalsnapshots 2021-04-01-142742 # deletes 1 snapshot

tmutil deletelocalsnapshots /   # deletes all the snapshots

Also see:

    diskutil apfs listSnapshots /

Applications -> Utilities -> Terminal

    sudo du -hx "$HOME" /var/* /opt/* /tmp/* | sort -h  # This will take a few minutes

The 'du' (disk usage) command will show storage being used in every

folder under your Home Folder and the /var & /opt folders. After

checking for local APFS snapshots, there is a reasonable possibility

your Home Folder tree is where most of the storage is being used. You

can specify other starting folders.

Manage Storage

What is “Other” storage on a Mac, and how can I clean it out?

Free up storage space on your Mac

OmniDiskSweeper Safe to use

GrandPerspective 

How to delete Time Machine snapshots on your Mac

See used and available storage space on your Mac

Locate backups of your iPhone, iPad, and iPod touch

The final word from Apple on Managing the " Other " Category

Other: Contains files that don’t fall into the categories listed here. This category primarily includes files and data used by the system, such as log files, caches, VM files, and other runtime system resources. Also included are temporary files, fonts, app support files, and plug-ins. You can't manage the contents of this category. The contents are managed by macOS, and the category varies in size depending on the current state of your Mac.

Quick fix. The issue did not occur over night but over time.

Fast fix - erase the drive and reinstall form zero. Only migrate the User Account and nothing more. Reinstall all applications as new

Not what one wants to hear but does qualify for Quick Fix

How many times has this computer been upGraded since it was First Setup as New ?

The accumulated effects of each upGrade, until now, plus all the Software Installed and or Removed will take its' toll on the Defined Drive Capacity.

The really danger if left unattended, the user will eventually have a great deal of time to ponder and lament why the computer Ceases to Function at all.

As mentioned earlier - that can happen and then there is No Choice but some radical Actions will be required.

it is suggested to keep at least 15%  to 20% of the Drive Total Capacity as Empty Space for good operations of the computer and for additional updates to download, expand and install.

IMHO, there has been enough advise offered for the User ( you ) to make an informed choice what  the next course of action is required to possibly fix this computer issue.

The suggestions have been put forth on a volunteer basis, in good faith and in the best interests of the computer

I'm going to say it probably was okay to delete, being that it's a log file and may just be recreated eventually by the app.

But to know more, I suggest you visit the Adobe support site I linked above and post any questions there.

The Initial Issue, outlined much earlier in this question remains and not really fixed IMHO

A " Quick Fix " for a Long Time unattended to issue will lightly only buy the user some time before the same old issue will rear its' head again - IMHO.

They have been cautioned very specifically what the consequences can be.

Which Drive is under discussion?

I see 3 External Drives and 1 Internal Drive

The Internal Drive appear ok for Empty Space

The computer may not crash but it may STOP booting up at all - period