De Lancre

Well, ackshually, it’s still a dragon.

Super frustrating

Honestly, by working in IT you may found out, that every soft suck in some way or another. Windows - constantly broke itself by updates\not working as intended in the first place + frustrating UI\UX decisions; Linux too complicated and don’t user friendly enough beyond “install firefox > use firefox > turn off pc”, also breaks down at time; Mac OS too closed source, to the point when to install some regular soft like wine you need to “unlock” your OS and reboot PC after some tinkering, also hackintosh almost death at this point, also poor apple decisions about feature set support, like recent drop of 32 bit applications or not supporting Vulkan, or dropping support of openGL and etc., also weird course about gaming support, it’s like they change their mind every damn month about it, so almost no game publishing company wanna work with them.

Everything sucks man, seriously. At this point it’s just “pick your poison”.

looking for a system that scans my existing games, gives a “yes it all works” or “no and here’s why”, that I can use to actually migrate

Well, you can connect your steam account to protondb and tap on “explore” button. That will not cover any software\games, but at least something. Altho, I would say: why you even want to switch at this point? Like, if you can withstand windows bullshitery but not linux bullshitery - stay on windows mate, no one will judge you. That why I staying on linux for example, even tho my work as junior system administrator mostly requires me to work with windows. I just can’t go to home, boot my pc and acknowledge the fact, that windows “updated” driver of my 7900xtx and I can’t play damn minecraft for 10 minutes before bed, cause I need to spend at least 20-30 minutes to fix that shit. I just can’t. Yes, my arch linux may broke on occasion cause of update or smth like that, but at least I have full control about that. And if something happens, it’s usually cause you decided to do something, not cause Microsoft decided silently “fix” their security issue in “Print Spooler” and broke all shared printers in the facility I working in.

gta5 (buggy)

Not sure about that one, but protondb stated, that it “gold”. Also, reports saying that even online works just fine.

the division 2 (anticheat)

Works almost a year already, cause game using “easyanticheat”, and proton supports it now, but devs need to change lib in their game manually, so not every game works, sadly.

entirety of Forza Horizon 3+4 and Halo Wars 2

Forza works just fine, cause you can install it from steam, I played 4 part myself not long ago. Not sure about Halo Wars tho, never played it. But “Halo Wars: Definitive Edition” is on steam and have platinum support level on protondb.

I want to say watch dogs legion (uplay)

First of all, proton is “just” an settings and patches on top of regular wine, that was around for ages. Yes, you can use it outside of steam (altho, that is not recommended by several reasons, and instead it’s recommended to use smth like wine-ge), so yes, by using various tools like Lutris, Bottles, etc. it is possible to install any existing launcher. More then that, community so sick cause of that launchers, that it created it’s own for GOG and Epic, called heroic launcher. As myself, I playing on regular basis a few games from there: Battlefield 1\5, StarWars: Battlefront 2, Control and few others. Of course even something older like Mass Effect will work just fine. That being said, I use braindamaged strat by installing any needed game by steam and proton itself, via “add other game to steam library” button. Yes, pirated games or even Origin launcher can be installed this way, but lutris usually easier.

NFS 2 through Most Wanted (2012), GTA 3 / VC / SA, Midtown Madness 1+2, System Protocol One, TDU 1+2 (with third-party multi-player support thru TDU World launcher)…

Tl:dr All old games mostly works fine or better on linux, cause of wine being smth like windows own “legacy support” thing. Hard part is installing and patching or running thru mod launchers. It’s usually in territory of “advanced users”, but tools like bottles can help. Only exception, if mods using just dll or replacing some textures, then installing will be exact as on windows. There also an official beta mod manager for nexus mods, for example, so modding smth like skyrim is now much easier, then before.

Any examples maybe?