Tested and working process in my lab current version VCF 4.5.2 and upgrading to VCF 5.2.1 using offline bundle.

VCF 5.2.1 Bom
https://techdocs.broadcom.com/us/en/vmware-cis/vcf/vcf-5-2-and-earlier/5-2/vcf-release-notes/vmware-cloud-foundation-521-release-notes.html#GUID-bea9c4f4-f376-4a63-9787-114a8b767ed2-en_id-0ca57a6f-9a25-40f4-d248-8489e66cf554

Offline bundles
https://docs.vmware.com/en/VMware-Cloud-Foundation/5.2/com.vmware.vcf.vxrail.doc/GUID-8FA44ACE-8F04-47DA-845E-E0863094F7B0.html

Process
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1. download bundle transfer utility for VCF 5.2.1 from the Broadcom page support page (under VMware Cloud foundation > 5.2.1 > drivers and tools tab)
2. Unzip lcm-tools-prod.tar.gz on your computer (windows) may throw some errors when unzipping it that can be ignored
3. Downloads to your computer

Command to download bundles
lcm-bundle-transfer-util --download "withCompatibilitySets" --outputDirectory c:\temp\lcm5.2.1 --depotUser kad@gmail.com --sv 4.5.2.0 --p 5.2.1.0
These are the bundles required this doesn't include load balancer or Aria products - seven in total
bundle-133762, bundle-133763, bundle-202281, bundle-133760, bundle-133765, bundle-133764, bundle-133766

Download the manifest file. location C:\Users\/PROD2/evo/vmw
./lcm-bundle-transfer-util --download --manifestDownload --depotUser kad@gmail.com

Download the compatibility data. - C:\Users\PROD2\evo\vmw\Compatibility\VmwareCompatibilityData.json
./lcm-bundle-transfer-util --download --compatibilityMatrix --depotUser kad@gmail.com

Download the vSAN HCL file. - C:\Users\PROD2\vsan\hcl\all.json
./lcm-bundle-transfer-util --vsanHclDownload 


You should at the end have.
all.json
VmwareCompatibilityData.json
lcmManifest.json
bundle download

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4. Bundle Transfer Utility to sddc manager
Copy lcm-tools-prod.tar.gz to sddc manager appliance /nfs/vmware/vcf/nfs-mount/ using WinSCP as user vcf
login as vcf via ssh
su
make directory using mkdir /opt/vmware/vcf/lcm/lcm-tools
copy lcm-tools-prod.tar.gz to /opt/vmware/vcf/lcm/lcm-tools/
cp /nfs/vmware/vcf/nfs-mount/lcm-tools-prod.tar.gz /opt/vmware/vcf/lcm/lcm-tools/
cd /opt/vmware/vcf/lcm/lcm-tools/
tar -xvf lcm-tools-prod.tar.gz
cd /opt/vmware/vcf/lcm/
chmod -R 775 lcm-tools
chown -R vcf_lcm:vcf lcm-tools

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5. manifest upload to sddc manager
copy  the manifest file to sddc manager using WinSCP as vcf user
ssh to sddc manager as vcf user
su
chmod -R 775 lcmManifestv1.json
chown -R vcf_lcm:vcf lcmManifestv1.json
Run as VCF user
make directory using mkdir /home/vcf/manifest/lcm/manifest/v1/
cp lcmManifest.json /home/vcf/manifest/lcm/manifest/v1/

Run below as VCF user
cd /opt/vmware/vcf/lcm/lcm-tools/bin/
./lcm-bundle-transfer-util --update --sourceManifestDirectory /home/vcf/manifest/ --sddcMgrFqdn sddc-manager.vcf.sddc.lab --sddcMgrUser administrator@vsphere.local
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6. 
Upload the compatibility files.
login as vcf user on to sddcM appliance
make directory using mkdir directory path /nfs/vmware/vcf/nfs-mount/vcf5.2.1/Compatibility/
copy VmwareCompatibilityData.json to the Compatibility folder
cd /opt/vmware/vcf/lcm/lcm-tools/bin/
run the below as a vcf user
./lcm-bundle-transfer-util --update --compatibilityMatrix --inputDirectory /nfs/vmware/vcf/nfs-mount/vcf5.2.1 --sddcMgrFqdn sddc-manager.vcf.sddc.lab --sddcMgrUser administrator@vsphere.local

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7. Upload the HCL file. (this may throw a error if your sddc manager is on a lower version "ERROR: Cannot upload vSAN HCL to SDDC Manager versions below 5.1.0.0." may need to do it later)
login as vcf user on to sddcM appliance ssh
make directory using mkdir directory path /nfs/vmware/vcf/nfs-mount/vcf5.2.1/vsan/hcl
copy the all.json to /nfs/vmware/vcf/nfs-mount/vcf5.2.1/vsan/hcl via WinSCP
cd /opt/vmware/vcf/lcm/lcm-tools/bin/
./lcm-bundle-transfer-util --vsanHclUpload --inputDirectory /nfs/vmware/vcf/nfs-mount/vcf5.2.1/vsan/hcl/all.json --sddcMgrFqdn sddc-manager.vcf.sddc.lab --sddcMgrUser administrator@vsphere.local

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8. Upload the bundle directory.
copy bundle directory downloaded lcm5.2.1 to sddcM appliance /nfs/vmware/vcf/nfs-mount/vcf5.2.1/
ssh to sddc manager
login as vcf
switch to su
chmod -R 0777 /nfs/vmware/vcf/nfs-mount/vcf5.2.1/lcm5.2.1/
switch to vcf user
cd /opt/vmware/vcf/lcm/lcm-tools/bin/
./lcm-bundle-transfer-util --upload --bundleDirectory /nfs/vmware/vcf/nfs-mount/vcf5.2.1/lcm5.2.1

By Kader