I have shared a few tunes. Given how rivals works I may not be judging them based on laptimes / world rankings like was possible on FH3.
Posting this from memory lol, will update / correct later.
1992 Ford Escort Cosworth rally tune
Opel Mantra Rally Tune - really good for the current seasonal trial
Lamborghini Sesto Forzathon Live tune (I did not necessarily tune it for that but its my go to car lol - it drifts, goes quick etc)
HDT VK Commodore tune from the first dirt rivals event - I assume my build is wrong but its a handy rally tune
Alfa 8C FE road tune - a little underpowered but glued to the road.
Honda NSX 1992 road tune
Nismo GT-R LM Forza Edition
I am not yet up with the best builds for FH and its harder to test given I used to use rivals events but will keep at it.
If anyone wants specific cars tuned for specific purposes out of road, dirt, cross country please post in this thread.