I had a long call with Apple support.
One, they say they still "officially" support Time Capsule configurations. The person made a statement that Time Capsule can only be doing one backup at a time. Shows how poor Apple support is. I had been using a Time Capsule for years for backing up two Macs. Never had to consider making sure only one was doing a backup. These kind of statements from Apple Support really irk me.
I hadn't thought about that Time Capsule runs AFP. I had built a Linux TimeCapsule server with RAID 5 over 10 years ago using the open source AFP implementation. Wonder if it would still work today?
I have gotten the Linksys external drive configuration to work. Have to mount it on my MAC using Go Connect to Server. Once mounted, Time Machine allows me to select it as a disk. The configuration seems to have no issues working with my M1 based MAC running Ventura. It never finished the first backup on my Intel Mac running Ventura. Is there anything in the M1 silicon that supports networking at the hardware level?
I now have the first backup on my Intel MAC.
Apple support says they don't officially support Time Machine over SMB to a linksys external drive. That seems counter to this article (Types of disks you can use with Time Machine on Mac - Apple Support). This statement so indicative of the arrogance of Apple and the dysfunction of who the company is today. At one point the Apple support guy made the statement "Why should Apple test that configuration? It should be up to the devices that want to work with Apple products?" This statement from the most valuable company in the world by Market Cap that has more cash in the bank than many countries. They no longer really care about making sure users can easily backup their MACs on a network drive. Linksys is not their product.
What's ridiculous about this statement is that Apple has to test with Linksys for Wifi compatibility with every MAC. It would be ridiculous for them to say they don't officially support Linksys as a Wifi access point. They only official support the Time Capsule as a Wifi access point. It would be trivial for them to test the external drive configuration with Linksys and ideally work with Linksys to make sure it works.
One issue with Linksys is that they don't support the current Apple default AFPS disk format. Why has Apple not worked with Linksys to enable that. Linksys does support the discontinued Mac OS Extended (Journaled) format file system.
Its time for all users to call out Apple for their arrogance today especially on features like Time Machine. Time Machine was one of the reasons why using Mac products in the past was so easy compared to Microsoft. Now Apple (at least from an Apple support perspective) seems to not care.