The latest update to the game features cross-platform matchmaking, but not for private lobbies. Full details can be found here…

https://dirtgame.com/dirt5/news/dirt-5-free-red-bull-update-may-11

We have no plans, at the moment, to add additional features to this element of the game.

Wheel support was added to the game in update 2.00. Full details appear here…
Wheel Support Options

Additional support for Fanatec wheels was added in the 4.04 patch…

Patch notes

NOTE. The links on this page will take you to external websites, which are not affiliated with Codemasters.

You can check if there are any reported server issues on our Twitter feeds…

Dirt Game
Formula One Game
Grid Game

If there are no reported issues with our servers then we can also check your platform’s (PSN, Xbox, Steam etc) status from the following links…
Playstation
Xbox
Steam
Stadia

For further troubleshooting, please ensure that your connection is unrestricted and all ports are open as per the advice on the following links….

Xbox One

PS4

PC/Steam

You will also need to open ports TCP and UDP port 3074.

PC users should also ensure that you have fully updated Windows (including all service packs). We recommend using Windows 10 for all games that support this version of Windows.

DIRT 5 offers console players a free upgrade option, meaning if you purchase the game on Xbox One or PlayStation 4, you can play an optimised version of DIRT 5 for the corresponding new consoles, at no additional cost.

Full details can be found here…

Free Next Gen Upgrade

Minimum:

Requires a 64-bit processor and operating system
OS: 64-Bit Windows 10 (18362)
Processor: AMD FX 4300 / Intel Core i3 2130
Memory: 8 GB RAM
Graphics: AMD RX 480 (DirectX12 Graphics Card) / NVIDIA GTX 970
DirectX: Version 12
Network: Broadband Internet connection
Storage: 60 GB available space
Sound Card: DirectX Compatible
Additional Notes: PC audio solution containing Dolby Atmos® required for Dolby Atmos playback.

Recommended:

Requires a 64-bit processor and operating system
OS: 64-Bit Windows 10 (18362)
Processor: AMD Ryzen 3600 / Intel Core i5 9600K
Memory: 16 GB RAM
Graphics: AMD Radeon 5700XT / NVIDIA GTX 1070 Ti
DirectX: Version 12
Network: Broadband Internet connection
Storage: 60 GB available space
Sound Card: DirectX Compatible
Additional Notes: PC audio solution containing Dolby Atmos® required for Dolby Atmos playback.

All Trophies should now be working normally but, if you started progress before the last update to the game, some may need further play to unlock. If you continue to play the game in the different modes, therefore, you should unlock any Trophies you should have received.

Any trophies linked to a particular vehicle can often be triggered by using that vehicle in arcade mode.

Can you locate your My Games folder. E.g.

C:\Users\[your username]\Documents\My Games\

If any of the text in this path uses symbols, or non-standard or non-western characters (e.g. é or ä, or Chinese/Korean/Japanese/Greek/Russian/Arabic) then this will cause this issue.

If so, please can you create a new Windows username that only features standard western characters and use this to play the game.

A) To play two player split screen on Xbox, please do as follows:

1) Ensure that both controllers are recognised by the console and that the Xbox symbol light is lit on both (Series S and X users may have to plug the second controller into the front USB port). You will need to have at least two users (gamertags) created on your console and a controller assigned to each.
2) Once in the game press the View button on the second controller and choose the gamertag (which must be different from player one). You should see a message saying the a player has joined the game.
3) Go to the arcade option of the game. If Time Trial is greyed out then the game has registered that there are two players wishing to play. If it is not greyed out repeat step 2)
4) Choose freeplay, setup the options you want for the game and then start the game. You should have two player mode enabled.

B) The instructions for PS4/PS5 are very similar except that you will need to ensure that your console is connected online, as the split-screen mode does not work if the console is offline.