Getting same issue here on Pop_OS! 22.04 after installing the latest build from the OpenRCT2 Nightly PPA (ppa:openrct2/nightly)
I used RCT Deluxe & RCT 2 Triple Thrill Pack files from GOG offline installers extracted using innoextract.
All other RCT 1 features work, such as title music, opening demo, etc., it just seems to be the rct1aa.ride.lay_down_trains object that is not loading properly. I was able to load RCT 1 scenarios that don't use this train type.
I did notice in the changelog that it says "Improved: [objects#329] Add RCT1AA lay-down coaster trains (for import only)", but I can't tell if that means it's in the latest nightly build or not.