Yup, like Gunja said.
There is a discord server around here somewhere (we don’t use enough of but does exist…) for flying with other GADC members in sims. Typically, if you wave in there someone will appear.
In addition to Liftoff and Velocidrone, there’s also Tryp FPV, Uncrashed, and FreeRider on steam:

For solo’s, I typically fly Tryp because it’s the prettiest. Uncrashed and Liftoff have similar graphics & feel, FreeRider I don’t actually remember so it probably wasn’t as good.
However, all of these sims expect a normal radio controller (not motion). If you’re going to stick with a motion controller, I suspect you’ll need to stick with the weird DJI mobile sim thingy.
The Avata 2 does cost a lot, but unless you’re building your own FPV drones (which requires a lot of watching Joshua Bardwell research), a decent “bind-n-fly” (pre-built, just bind it to your radio/goggles and fly) is only marginally cheaper. I own and recommend the Flywoo LR4 (for longer range/smooth flying) and the CineRace20 (for flying tracks/through obstacles), both set you back £390. In addition, you’d need more batteries (FPV batteries don’t last nearly as long as an Avata 2 battery would) and a charger for those batteries (they would not be charged by USB like the Avata 2’s are I believe).
Neither of the above would work with your motion controller, they’d need something like the RM Zorro/Boxer (or any other ELRS 2.4g radio), however they would work with the Integra Goggles.
My 2pence, if this is likely to be a 6-12 month “phase”, you may be better off staying with the DJI eco-system/Avata. If you/your son are likely to stick with it, return that motion controller if you can, get yourself a Boxer, get some stick time in the sims, pick a Bind n Fly sub-250g to get in the air, and build outwards on that initial gear (once you have radio, goggles, and charger, adding drones to your fleet is wayyyy easier).
If you have an xbox/Ps5 controller, you can play the sims with that, but there is a significant difference (throttle/left-vertical does not centre on a radio, but would centre on a game-controller).
EDIT: The discord server I mentioned; details and more sim recommendations here: Simulator Rip (Lift off, Velocidrone) Evenings 9/9:30pm