I've been playing for a while on an old phone (Samsung Galaxy S7) on single player and multiplayer LAN with my son on our perfectly functioning Wifi. For me, the performance has been adequate: Beautiful Skies, Smooth Lighting, Fancy Graphics turned on, 10 chunks settings (slightly over recommended for my poor hardware) giving 30+ fps in good conditions, no particular lag spikes. Following the 1.18.30 update last night, the game is unplayable. I have perhaps 5 fps, and bad input lag: it takes maybe 0.5 seconds from swiping over the screen until the character starts turning. When I touch forward, I have the time to raise my finger before the character starts moving. I've turned off all possible settings: Beautiful Skies, Smooth Lighting, Fancy Graphics, 5 chunks, but the bad performance doesn't change.

I have noted MCPE-154153 which may be related but the deterioration is much worse and the drop in fps is significant.

[Edit] Possible duplicate of MCPE-142934. It seems like this issue (RenderDragon) has been known since at least September 2021, reported for Windows 10 but comments about unplayable Android performance in beta since January 2022.

[1.18.31] The issue still persists, possibly it's even slightly degraded. The patch notes mention "Addressed various framerate hitches, particularly impacting less powerful mobile devices".