[Samsung Galaxy Watch 4] adfree:
META-INF\CERT.RSA
META-INF\CERT.SF
META-INF\com
META-INF\MANIFEST.MF
META-INF\com\android
META-INF\com\google
META-INF\com\android\metadata
META-INF\com\android\otacert
META-INF\com\google\android
META-INF\com\google\android\update-binary
META-INF\com\google\android\updater-script
SEC-INF\buildinfo.xml

boot.img.p
build_info.txt
dtbo.img
dynamic_partitions_op_list
file_contexts.bin
keystorage.bin
ldfw.img

modem.bin.p
odm.new.dat
odm.patch.dat
odm.transfer.list
optics.new.dat
optics.patch.dat
optics.transfer.list
plat_file_contexts
prism.new.dat
prism.patch.dat
prism.transfer.list
product.new.dat
product.patch.dat
product.transfer.list
sboot.bin

system.new.dat
system.patch.dat
system.transfer.list
tzar.img
tzsw.img
uh.bin
up_param.bin
vbmeta.img
vbmeta_system.img
vendor.new.dat
vendor.patch.dat
vendor.transfer.list

Files inside update.zip from SM-R875F...

buildinfo.xml in SEC-INF folder

<TOKEN>
<MODE TYPE="FOTA"/>
<APSOURCE version="AP_R875FXXU1BUH9_CL22353423_QB42369104_REV00_user_low_ship_MULTI_CERT_meta_WATCH_OS11.tar.md5"/>
<CSCSOURCE version="CSC_OMC_OXA_R875FOXA1BUH9_CL22353423_QB42369128_REV00_user_low_ship_MULTI_CERT.tar.md5"/>
<CPSOURCE version="CP_R875FXXU1BUH9_CP20014857_CL22353423_QB42369104_REV00_user_low_ship_MULTI_CERT.tar"/>
<APTARGET version="AP_R875FXXU1DUJA_CL22779555_QB44913704_REV00_user_low_ship_MULTI_CERT_meta_WATCH_OS11.tar.md5"/>
<CSCTARGET version="CSC_OMC_OXA_R875FOXA1DUJA_CL22779555_QB44913716_REV00_user_low_ship_MULTI_CERT.tar.md5"/>
<CPTARGET version="CP_R875FXXU1DUJA_CP20697872_CL22779555_QB44913704_REV00_user_low_ship_MULTI_CERT.tar"/>
<DIGEST value="480e3d594339cc95130966f7cfadb498594d96936efed3b682dac976d05a4403"/>
<CREATE date="20211018"/>
<VERSION value="20706693-1.8-30"/>
<INDEX value="1.1"/>
</TOKEN>

build_info.txt

model_name=SM-R875F
source_ap_file=AP_R875FXXU1BUH9_CL22353423_QB42369104_REV00_user_low_ship_MULTI_CERT_meta_WATCH_OS11.tar.md5
source_bl_file=BL_R875FXXU1BUH9_CL22353423_QB42369104_REV00_user_low_ship_MULTI_CERT.tar.md5
source_cp_file=CP_R875FXXU1BUH9_CP20014857_CL22353423_QB42369104_REV00_user_low_ship_MULTI_CERT.tar.md5
source_csc_file=CSC_OMC_OXA_R875FOXA1BUH9_CL22353423_QB42369128_REV00_user_low_ship_MULTI_CERT.tar.md5

target_ap_file=AP_R875FXXU1DUJA_CL22779555_QB44913704_REV00_user_low_ship_MULTI_CERT_meta_WATCH_OS11.tar.md5
target_bl_file=BL_R875FXXU1DUJA_CL22779555_QB44913704_REV00_user_low_ship_MULTI_CERT.tar.md5
target_cp_file=CP_R875FXXU1DUJA_CP20697872_CL22779555_QB44913704_REV00_user_low_ship_MULTI_CERT.tar.md5
target_csc_file=CSC_OMC_OXA_R875FOXA1DUJA_CL22779555_QB44913716_REV00_user_low_ship_MULTI_CERT.tar.md5

current_version=R875FXXU1BUH9/R875FOXA1BUH9/R875FXXU1BUH9
updated_version=R875FXXU1DUJA/R875FOXA1DUJA/R875FXXU1DUJA
dummy_version=R875FXXU1DUJA.DM/R875FOXA1DUJA/R875FXXU1DUJA
source_os_version=11
target_os_version=11
source_ap_build_date=Wed Aug 11 20:25:33 KST 2021
target_ap_build_date=Mon Oct 18 09:56:13 KST 2021
is_manual_build=N
security_patch_version=2021-11-01
csc_information=OXA(ATO AUT BGL BTU CPW DBT EUA EUB EUD EUE EUF EUR ITV LUX NEE PHE PHN ROM SEB SEE SIO TPH XEF XEH XEO XEZ XSK)

Haha... funny look at Pics taken from up_param.bin

I have entered g.co/ABH

Edit 1.

Some stupid Google search... leads to these Links:

Non-A/B system updates | Android Open Source Project

source.android.com

Block-based OTAs | Android Open Source Project

source.android.com

Inside OTA packages | Android Open Source Project

source.android.com

Android Verified Boot 2.0

Edit 2.

Maybe Tools... not tested yet...

https://xdaforums.com/t/dev-sdat2img-1-1-img2sdat-1-7-o-unpack-re-pack-android-dat-files.2978952/

Edit 3.

Tested short something under Windows... but maybe outdated...

Maybe with Linux... found something with Android 9 support... maybe...

https://xdaforums.com/t/tool-android-rom-repack-tools.3763986/

Edit 4.

Maybe closer.... Windows Version found...

https://xdaforums.com/t/8-3-2019-updated-android-img-tools-upto-android-9-0.3891887/