i'm pretty sure it does not. Flatpak uses bubblewrap for its sandboxing.
Firejail is a separate project.

firejail always launches in a separate PID namespace, meaning the process does not have access to any other processes you have running.
using the parameter "--net=none" the process will use a separate network namespace, where no network interface is configured. ie. forbidding network access to anything.
using "--private=${HOME}/games/xxxx" will mount the given directory ontop of your home directory, so the process can't read or write anything to your ${HOME}. Instead it treats "${HOME}/games/xxxx" as its home directory.

is that the sort of locking down that you are looking for ?

Not if you use the --join option.

yeah, kinda. Hide other processes, username of current user and name of host, block internet access (or restrict it to certain interface. Say, allow only eth0). Hide every directory except ones that necessary to work (/usr/lib and such. Everything that isnt allowed directly is forbidden). Allow application to only write stuff into its config/savefile folders

Game: Rusty Lake Hotel
Version: GOG v.1
Installer MD5: a6121ae5cd353c8e86342e7b45cef9b4 - setup_rusty_lake_hotel_gog-1_(30681).exe

Distro: Linux Mint 19.1 Tessa 64-bit MATE
Kernel version: 4.15.0-55-generic x86_64
Graphics card: Intel HD Graphics
Wine version(s) tested: 4.10 staging
WineHQ AppDB link: none

Install notes: Installs correctly, except 4 traditional runtime errors ending GOG installer (however the final result is "installation successful"). No errors, nor warnings in game itself. No libraries needed.
How well does it run: Perfect. No issues. The game has been completed.
Details: I'm using budget laptop with Intel Pentium CPU 3550M 2×2.30GHz + integrated Intel HD Graphics on board.

Probably too late and probably my answer add nothing, as I'm the one who made that Wine HQ report, but - yes, sure, the game is perfectly playable on Linux, small issues does not affect overall experience and I can definitely recommend the game, I really liked it, smart and challenging.

Thanks for confirmation!

The game is still on GOG, so it's not too late. Thanks! I'll add it to my wishlist, waiting for a good sale. The only part which scares me is the "challenging". :P

I still want to know about Bloodstained.

well, that's challenging if you're not some hardcore strategy gamer. the game has limitation for healing and enemies can deal more damage than you can heal. I'd suggest you to watch some walkthroughs to get an idea if it's for you. If you played previous title - Age of Decadence - you'll find it very similar to Dungeon Rats (the key difference is party based game vs solo).

According to youtube videos, it does work in Linux, some users reported issues with an Nvidia GPU see here: https://github.com/doitsujin/dxvk/issues/1099

checked winedb recently and found that somebody has managed to finally run xanadu next under wine: https://bugs.winehq.org/show_bug.cgi?id=40643

Can anybody there confirm it? Im currently unable to check by myself

Game: Rusty Lake Roots
Version: GOG v.1
Installer MD5: dae526768d941d55dc80700cc4d3a678 - setup_rusty_lake_roots_gog-1_(30681).exe

Distro: Linux Mint 19.1 Tessa 64-bit MATE
Kernel version: 4.15.0-55-generic x86_64
Graphics card: Intel HD Graphics
Wine version(s) tested: 4.10 staging
WineHQ AppDB link: none

Install notes: Installs correctly, except 4 traditional runtime errors ending GOG installer (however the final result is "installation successful"). No errors, nor warnings in game itself. No libraries needed.
How well does it run: Perfect. No issues. The game has been completed.
Details: I'm using budget laptop with Intel Pentium CPU 3550M 2×2.30GHz + integrated Intel HD Graphics on board.

Game: Rusty Lake Paradise
Version: GOG v.1
Installer MD5: 5ff0a14bcc068232cb9948987474b503 – setup_rusty_lake_paradise_gog-1_(30704).exe

Distro: Linux Mint 19.1 Tessa 64-bit MATE
Kernel version: 4.15.0-55-generic x86_64
Graphics card: Intel HD Graphics
Wine version(s) tested: 4.10 staging
WineHQ AppDB link: none

Install notes: Installs correctly, except 4 traditional runtime errors ending GOG installer (however the final result is "installation successful"). No errors, nor warnings in game itself. No libraries needed.
How well does it run: Perfect. No issues. The game has been completed.
Details: I'm using budget laptop with Intel Pentium CPU 3550M 2×2.30GHz + integrated Intel HD Graphics on board.

How do you install a game with multiple installers? When I try to use innoextract for a .bin file it returns with an error, same thing happens when I use wine.

Just use the exe file.

How exactly do I do that? Is it part of the install setup?