After running into some issues ([avr-gcc] mingw-w64-i686-avr-toolchain fails to install: Maximum file size exceeded · Issue #2585 · msys2/MSYS2-packages · GitHub) and solving them, I was able to compile simavr in 32-bit mode.
See https://drive.google.com/file/d/1vCoSAP9eQygr-IpVIaGYS-1yaE0eJW2h/view?usp=sharing for a download. You should grab the simavr.exe from it and put it in C:\Users\<user>\.platformio\packages\tool-simavr\bin\, replacing the old one. The zip also contains a firmware.hex test firmware.
>simavr --mcu atmega328p --freq 16000000 -v firmware.hex
Loaded 1 section of ihex
Load HEX flash 00000000, 1636
Hello, world!..
Hello, world!..
Hello, world!..
(Ctrl+C to abort)