I used Codex to investigate and locally fix this on my machine. I know
maintainers are dealing with a lot of low-quality AI-generated
reports/patches, so I am sharing this only as diagnostic information,
not as an upstream-ready patch.

Device:
- Realtek USB2.0 Finger Print Bridge
- USB ID: 2541:fa03

Versions:
- fprintd: 1.94.5-4
- libfprint: 1:1.95.1+tod1-0ubuntu1

Findings:
- Enrollment reached all 8 stages, then fprintd crashed.
- The crash looked like fprintd was logging a GError whose message pointer was 
invalid.
- In libfprint/drivers/realtek/realtek.c, the Realtek driver appears to pass 
SSM-owned errors from fpi_ssm_get_error(ssm) into completion APIs that take 
ownership.
- Changing those paths to use fpi_ssm_dup_error(ssm), or 
g_steal_pointer(&error) for callback-owned errors, stopped the crash.

After that, enrollment failed with “Current fingerprint is duplicate!”.
This machine dual-boots Windows and the sensor stores templates on-
device, so this may have been a stale/Windows-created template.

The attached local patch also made fprintd’s existing garbage-
collection/retry path work for this case. With it, enrollment completed
successfully and fprintd-list showed my right-index-finger enrolled.

I have attached realtek-fa03-enroll-fix.patch as the exact local
workaround that fixed my machine. It probably needs maintainer review,
especially the duplicate/DATA_FULL and on-device deletion behaviour.


** Patch added: "My patch, workaround"
   
https://bugs.launchpad.net/ubuntu/+source/libfprint/+bug/2151131/+attachment/5976797/+files/realtek-fa03-enroll-fix.patch

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https://bugs.launchpad.net/bugs/2151131

Title:
  Fingerprint enrollment segfaults on Realtek 2541:fa03 since libfprint
  1.95.1

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