PSX & variants
PSX, PS2 TV & special variants
Beyond the standard fat and slim consoles, Sony produced a few unusual PlayStation 2 variants that behave differently and deserve a mention.
PSX (DESR series)
The Japan-only PSX was a combined PS2 and digital video recorder with a hard drive and a completely different XMB-style interface. It is a collector's curiosity with its own niche homebrew scene, and it is not modded the same way as a standard PS2.
PS2 TV / integrated units
Sony and partners also embedded PS2 hardware into a small number of integrated devices. These typically use late boot ROMs similar to the final slims, so the FreeDVDBoot route is the safe assumption.
Rule of thumb
For any unusual variant, identify the boot ROM first and lean on FreeDVDBoot plus PS2BBL/OpenTuna, which are the most broadly compatible entry methods.