The one that worked with stability was:
Silicon Power brand : FBC-SP008GLSTU160N02
Earlier, had one from Timetec brand : 76TT16NUSL2R8-8G, which boots and kind of runs, but there were occasional crashes. & the router goes dead. Not sure of the reason, it passes memtest when the modules was tested on a a desktop with a dimm to sodimm adapter, but fails memtest when run from within the router. So it look like the routers' mobo is not that happy with the module.
dmesg output after RAM upgrade
---<<BOOT>>---
Copyright (c) 1992-2023 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
The Regents of the University of California. All rights reserved.
FreeBSD is a registered trademark of The FreeBSD Foundation.
FreeBSD 14.2-RELEASE-p2 stable/25.1-n269701-7c59d89f8cd SMP amd64
FreeBSD clang version 18.1.6 (https://github.com/llvm/llvm-project.git llvmorg-18.1.6-0-g1118c2e05e67)
VT(vga): resolution 640x480
CPU: Intel(R) Celeron(R) CPU N3350 @ 1.10GHz (1094.40-MHz K8-class CPU)
Origin="GenuineIntel" Id=0x506c9 Family=0x6 Model=0x5c Stepping=9
Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
Features2=0x4ff8ebb7<SSE3,PCLMULQDQ,DTES64,DS_CPL,VMX,EST,TM2,SSSE3,SDBG,CX16,xTPR,PDCM,SSE4.1,SSE4.2,x2APIC,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,RDRAND>
AMD Features=0x2c100800<SYSCALL,NX,Page1GB,RDTSCP,LM>
AMD Features2=0x101<LAHF,Prefetch>
Structured Extended Features=0x2294e283<FSGSBASE,TSCADJ,SMEP,ERMS,NFPUSG,MPX,PQE,RDSEED,SMAP,CLFLUSHOPT,PROCTRACE,SHA>
Structured Extended Features3=0x2c000000<IBPB,STIBP,ARCH_CAP>
XSAVE Features=0xf<XSAVEOPT,XSAVEC,XINUSE,XSAVES>
IA32_ARCH_CAPS=0x1<RDCL_NO>
VT-x: (disabled in BIOS) PAT,HLT,MTF,PAUSE,EPT,UG,VPID,VID,PostIntr
TSC: P-state invariant, performance statistics
real memory = 10737418240 (10240 MB)
avail memory = 10167812096 (9696 MB)