Sun SPARC
Like most engineers of a certain age, I've used a number of Sun products
in a professional and educational capacity.
This popularity made them exceedingly easy to find and inexpensive to
purchase and support.
Installing Linux or NetBSD over the network was a snap with Sun's Open Boot predecessor to OpenFirmware. For a while I was running the Suns I had at the time entirely diskless, booting them with DHCP/BOOTP/TFTP and providing shared root file systems via NFS from another Linux server.
As interest in the museum waned, I donated all my Sun hardware back to Goodwill ComputerWorks where, hopefully, another enthusiast could donate a little money and keep them running.