Steps I try to solve / investigate this problem.

gentoo-gnucash-not-save-preference.txt (text/plain), 6.64 KB, created by BrianHsu on 2021-11-23 03:19:17 UTC

# GnuCash is not installed
brianhsu@RyzenDesktop ~ $ which gnucash
which: no gnucash in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/opt/bin:/usr/lib/llvm/13/bin)

# There is no GnuCash related settings under /usr/share
brianhsu@RyzenDesktop ~ $ ls -l /usr/share/glib-2.0/schemas/org.gnucash
ls: cannot access '/usr/share/glib-2.0/schemas/org.gnucash': No such file or directory
brianhsu@RyzenDesktop ~ $ ls -l /usr/share/glib-2.0/schemas/gschemas.compiled
-rw-r--r-- 1 root root 76269 Nov 22 21:25 /usr/share/glib-2.0/schemas/gschemas.compiled

# The /usr/local/share only contains settings for another unrelated program
brianhsu@RyzenDesktop ~ $ ls -l /usr/local/share/glib-2.0/schemas
total 8
-rw-r--r-- 1 root root  556 Nov 22 20:01 gschemas.compiled
-rw-r--r-- 1 root root 1542 Nov 22 19:57 org.regolith-linux.remontoire.gschema.xml

# The XDG DATA DIRS only contains /usr/local/share and /usr/share
brianhsu@RyzenDesktop ~ $ echo $XDG_DATA_DIRS
/usr/local/share:/usr/share

# There is no gnucash configuration in dconf
Screenshot: https://imgur.com/OLQkBWT.png

# There is no related (old or new) setting in gsettings.
brianhsu@RyzenDesktop ~ $ gsettings list-keys org.gnucash.general
No such schema “org.gnucash.general”
brianhsu@RyzenDesktop ~ $ gsettings list-keys org.gnucash.general
No such schema “org.gnucash.general”
brianhsu@RyzenDesktop ~ $ gsettings get org.gnucash.general prefs-version
No such schema “org.gnucash.general”
brianhsu@RyzenDesktop ~ $ gsettings get org.gnucash.GnuCash.general prefs-version
No such schema “org.gnucash.GnuCash.general”

# Switch to root and install GnuCash 4.8
RyzenDesktop ~ # emerge -pv gnucash

These are the packages that would be merged, in order:

Calculating dependencies... done!

[truncated...]

[ebuild  N     ] dev-db/libdbi-drivers-0.9.0-r1::gentoo  USE="sqlite -doc -firebird -mysql -oci8 -postgres -static-libs" 1,787 KiB
[ebuild  N     ] app-office/gnucash-4.8::gentoo  USE="debug gui nls quotes sqlite -aqbanking -doc -examples -gnome-keyring -mysql -ofx -postgres -python -register2 -smartcard -test" PYTHON_SINGLE_TARGET="python3_9 -python3_8 -python3_10" 14,336 KiB

RyzenDesktop ~ # emerge -pv gnucash

[truncated...]
>>> Installing (142 of 142) app-office/gnucash-4.8::gentoo
 * Updating icons cache ...                                                                                                                [ ok ]
 * Updating GSettings schemas ...                                                                                                          [ ok ]
 * Updating .desktop files database ...                                                                                                    [ ok ]
 * Updating shared mime info database ...                                                                                                  [ ok ]
 * Backup all financial files or databases before using GnuCash >=2.7.0!
 * 
 * GnuCash 2.7.0 introduced large changes in its file format and database
 * schema that WILL prevent you from reverting back to GnuCash 2.6.

>>> Recording app-office/gnucash in "world" favorites file...
>>> Auto-cleaning packages...
>>> No outdated packages were found on your system.

# After install, there did exist GnuCash settings in /usr/share
brianhsu@RyzenDesktop ~ $ ls -l /usr/share/glib-2.0/schemas/org.gnucash.*
-rw-r--r-- 1 root root 106095 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.deprecated.gschema.xml
-rw-r--r-- 1 root root  11335 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.dialogs.business.gschema.xml
-rw-r--r-- 1 root root   7026 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.dialogs.checkprinting.gschema.xml
-rw-r--r-- 1 root root    777 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.dialogs.commodities.gschema.xml
-rw-r--r-- 1 root root   1079 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.dialogs.export.csv.gschema.xml
-rw-r--r-- 1 root root  15196 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.dialogs.gschema.xml
-rw-r--r-- 1 root root    872 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.dialogs.import.csv.gschema.xml
-rw-r--r-- 1 root root   6570 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.dialogs.import.generic.gschema.xml
-rw-r--r-- 1 root root   2543 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.dialogs.import.qif.gschema.xml
-rw-r--r-- 1 root root   1951 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.dialogs.reconcile.gschema.xml
-rw-r--r-- 1 root root   4151 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.dialogs.sxs.gschema.xml
-rw-r--r-- 1 root root   1053 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.dialogs.totd.gschema.xml
-rw-r--r-- 1 root root    465 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.general.finance-quote.gschema.xml
-rw-r--r-- 1 root root  29804 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.gschema.xml
-rw-r--r-- 1 root root   2806 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.history.gschema.xml
-rw-r--r-- 1 root root  12756 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.warnings.gschema.xml
-rw-r--r-- 1 root root   4055 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.window.pages.account.tree.gschema.xml
-rw-r--r-- 1 root root    674 Nov 22 21:57 /usr/share/glib-2.0/schemas/org.gnucash.GnuCash.window.pages.gschema.xml

# gsettings did exist
brianhsu@RyzenDesktop ~ $ gsettings list-keys org.gnucash.general
tab-position-top
auto-decimal-point
retain-days
[truncated...]

# There are also GnuCash entries in dconf-editor
Screenshot: https://imgur.com/hdJUI9X.png

# Switch back to normal user, checked there is no any GnuCash related config
# under my home directory.

brianhsu@RyzenDesktop ~ $ find . | grep 'gnucash'
brianhsu@RyzenDesktop ~ $ 

# Start GnuCash and testing
Screen Recording: 

# There do have some configuration under my home directory
brianhsu@RyzenDesktop ~ $ find . | grep 'gnucash'
./.config/gnucash
./.local/share/gnucash
./.local/share/gnucash/books
./.local/share/gnucash/books/gnucash.gnucash.gcm
./.local/share/gnucash/checks
./.local/share/gnucash/translog
./.local/share/gnucash/accelerator-map
./gnucash.gnucash

# There are two show-splash-screen under different path
brianhsu@RyzenDesktop ~ $ gsettings list-keys org.gnucash.GnuCash.general | grep 'splash'
show-splash-screen
brianhsu@RyzenDesktop ~ $ gsettings list-keys org.gnucash.general | grep 'splash'
show-splash-screen

# Both of them are set to true
brianhsu@RyzenDesktop ~ $ gsettings get org.gnucash.GnuCash.general show-splash-screen
true
brianhsu@RyzenDesktop ~ $ gsettings get org.gnucash.general show-splash-screen
true