There is no Linux like solution for android phone that runs Xserver and OpenJDK reliably. Samsung DEX emulation was the only usable solution, but that was killed off. Termux can not run OpenJDK, some weird issues with crashing.
Also most devices do not have enough cooling capacity, max performance can be only delivered in short bursts before CPU gets throttled down. If you hack it to run at full speed for hours, it freezes.
PI is simply the only option at this size, with enough CPU power and good Linux support.