First, let me say what you may already know- stock apps generally suck.
Thankfully, there are nice replacements out there that do a much better job.
Settings
Storage
Phone
Apps
(show system)
What are the largest, and can the caches be cleared?
This can save at least enough space to try to get some room to work with.
I try to maintain about 70% or less used internal space.
Because some phones include the system in their percentage, I use an app that shows the percentage used that is available to the user.
https://f-droid.org/en/packages/com.kgurgul.cpuinfo/
If you have an SD card, you will see three listed memory used percentages.
The first two are one and the same.
As replacement for clumsey stock utility apps, I use a catalog of apps from Simple Mobile Tools.
https://www.simplemobiletools.com/
For now, at least try the file manager and the gallery.
The gallery is a great video player as well.
https://f-droid.org/en/packages/com.simplemobiletools.filemanager.pro/
https://f-droid.org/en/packages/com.simplemobiletools.gallery.pro/
These two work seamlessly together and will make you wonder how you ever dealt with the rest.
Use them to move any personal files like pics, videos, and documents to the SD card.
After this, there is one cleaner app that tells the truth about cleaner apps, and does all that a cleaner app can actually do.
https://f-droid.org/en/packages/theredspy15.ltecleanerfoss/
Please be sure to go through all of the settings, and engage the whitelist.
This is a real cleaner and you must be sure that your valuanle files are not in its path.
You mentioned that 'everything is updated'.
When apps are updated, they grow.
Eventually, they get so big as to intrude upon your space- and eventually even the proper function of the device.
Be sure that Auto-Update in the PlayStore is turned off.
There are various reasons for this, but for now, in your case, you don't need updates for any apps that you don't use.
Speaking of which, if you have discovered suitable replacements for any stock apps, see if the stock ones can be disabled.
Do the same for any apps that you don't use.
Built in system apps can only be disabled, but user apps can be downright uninstalled.
When uninstalling, be sure to clear all data first.
This insures that all files and data of the app is gone.
These things can save a large amount of space.
Now check what CPU Info says again.
Let me know what your results are.
