"Unexpected error" & game crash occurs immediately when spawning. Caused when attempting to play Stoneblock 3 V1.7.0. Versions of REI & Rubidium used, for clarity:
RoughlyEnoughProfessions-forge-1.18.2-1.0.2.jar
RoughlyEnoughItems-8.3.594.jar
REIPluginCompatibilities-forge-8.0.46.jar
rubidium-0.5.5.jar

Full crashlog:
crash-2023-05-20_16.50.00-client.txt

As of typing this, I found I had the wrong version of Rubidium installed. It was 0.5.6 I should've used.