Did the IRA only hit legitimate targets during a war? Did they not, for example, set bomb a city centre with no particular strategic value or target?

The fact that a concealed bomb is used does not make it a terror attack. RF is at war with Ukraine, espionage, propaganda and production centres are legitimate targets. It would be not  be acceptable to bomb a supermarket, shell a Theatre or kill civilians, steal their property and mass-grave them.

I support the peaceful (read it again) right to self determination and, in general, a military defensive response against a military attack with the objective of reaching a durable peace. More so when a democracy or something that could become a true democracy is at war with a despot.