How to use older Mac with RAID for Time Machine

I have been trying unsuccessfully to use an older Mac on my LAN as a Time Machine repository for various other Macs around the house. Using RAID 0, I've created two pair of drives. Then using RAID 1, mirrored those.

My intention was to create partitions for each of the machines I want to back up. Disk Utility will not allow making partitions on the RAID drive. In another attempt, I created sparse bundle images both by the host machine and client machines, which could not be seen by the client computers. Mounting those images on the host machine allowed two of the four computers to see them and select them a Time Machine volumes. Those two seemed to make one backup but Time Machine on the client machines could not open them to see any of the previous backup.

Time Machine indicates that "Next backup: When disk is connected". Attempting to mount the sparse bundle from a client machine says "Resource temporarily unavailable."

The sparse bundle image created by the host on the internal RAID disk is able to use a mounted disk image (.dmg) for Time Machine backups while it does not see sparse bundles. Other computers online can see mounted disk images and sparse bundle files but cannot open/mount the sparse bundles even though permissions for myself and staff are set to rwx.

Is it possible to break up the RAID 1 (connecting two pair of drives) and then make partitions on the RAID 0, then reconnect the pairs? After several days of trying other options, I'm not sure what to try next.

Can anyone point me in the right direction for using an older Mac for a host for several other varied machines?

Host: macOS Mojave 10.14.6. primary drive PCI SSD. Drive bays contain RAID drives. Can use .dmg file on RAID for Time Machine backup.

Computer 1: macOS Big Sur 11.5.1. Single drive. Have connected mounted sparse bundle image (created by Computer 1 on mounted RAID drive) to Time Machine. See no other bundles. Only other option seen is full RAID drive.

Computer 2: macOS Sierra 10.12.6. Same as Computer 1.

Computer 3: macOS Snow Leopard 10.6.8 Single drive. Unable to create images on RAID. Can mount dmg file from RAID but Time Machine only recognized full RAID disk.

Computer 4: macOS Mojave 10.14.6. Single drive. Able to see RAID , mounted dmg specified for Computer 3, and personal home directory on Computer 1

Any assistance from someone doing something similar would be appreciated.