Distro: Debian bullseye
Controller: 8Bitdo SF30 Pro
Kernel used: The one included with debian bullseye
WINE version: Again, the one in debian bullsyey

Do you like, NEVER sysupgrade?
You make it sound like there is just ONE version for each used on EACH worldwide install of given Debian iteration :S (major facepalm)
Would it hurt you to check
uname -a
as well as
wine --version
?
:S

OK, here's the results:
Linux [hostname] kernel: 5.9.0-5-amd64 #1 SMP Debian 5.9.15-1 (2020-12-17) x86_64 GNU/LINUx
wine-5.0 (Debian 5.0-4)

Also, while I believe it's not software related, there's another controller issue I've been having when I try to press up, the controller will frequently register a diagonal, which is a problem in games like Celeste and Zelda 3. (Note that this problem isn't just specific to one computer; the versions stated are for the laptop I'm playing The Alliance Alive on.)

Well, off I go checking package dependencies (a hell if you will, but I'm a regular already [read through a major amount of ArchLinux documentation, took me several weeks of reading for multiple hours a day] so no biggie /s) - why? - since for example " wine-5.0 (Debian 5.0-4) " may very well not mean "100% vanilla Wine repo copy" (and for example since I know for a fact that ArchLinux optimises things here and there I also am aware some other distros do that too).

It could possibly be related to physical failure or problem.
If by any chance you were rough with the controller it could possibly result in PCB issues.
But that's not really possible to diagnoze over the internet (there is a bunch of software for dealing with joysticks and gamepads, it could potentially be tested, but of course it's up to you to decide).

P.S.
I'm sorry if I don't respond any time soon.
But I should still be able to respond within 24 h (or 96 h if I happen to run into IRL BS).

I recently installed Opus Magnum on my Manjaro system, and it went very well. The game plays fine. That said, it always starts on my second monitor, so I have to go into the settings, switch it to Windowed mode, move it to my primary monitor, and turn it back to full screen. I went looking for a simpler way to force the program to open on the correct monitor, and found the GOG startup script:

#!/bin/bash
# GOG.com (www.gog.com)
# Game

# Initialization
CURRENT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
cd "${CURRENT_DIR}"
source support/gog_com.shlib

# Game info
GAME_NAME="$(get_gameinfo 1)"
VERSION="$(get_gameinfo 2)"
VERSION_DEV="$(get_gameinfo 3)"

# Actions
run_game() {
echo "Running ${GAME_NAME}"
cd game
./"Lightning"
}

default() {
run_game
}

# Options
define_option "-s" "--start" "start ${GAME_NAME}" "run_game" "$@"

# Defaults
standard_options "$@"


Is there a way to modify this script (or some better way), to fix my monitor situation?

Try running arandr, and seeing which monitor is your primary monitor. This will allow you to change it as well (though it seems not to persist through reboot).

Let me guess:
it's your utmost top left screen?
Fyi in Linux screens are numbered from top left to down right (physical placement doesn't matter, what matters are GPU video plugs order as well as software xrandr settings).

Kept you waiting huh?
For starters you can use xboxdrv ( https://packages.debian.org/buster/xboxdrv it seems there is only a version in stable, in case of troubles you could try to selfcompile https://xboxdrv.gitlab.io/ also notice some links resources at the bottom of that page ).
I also found these:
https://www.reddit.com/r/8bitdo/comments/kkayi4/xboxdrv_config_file_for_sn30_pro_for_android/
https://steamcommunity.com/app/221410/discussions/0/558748653738497361/

Regarding wine, it doesn't seem like anything particularly relevant was released since
https://metadata.ftp-master.debian.org/changelogs//main/w/wine/wine_5.0.3-3_changelog
but it is of course good to be fairly up to date (tho I am not forcing you to update).
I hope you do have winetricks, and I cant vouch for any Debian-originated package modifications that could affect performance but using wine-staging is generally better in many cases.

Btw, there is a possibility you have some weird wine controller config.
I suggest you go into wine config and check that.

I do, and I used it to install corefonts (without it, text in The Alliance Alive is missing spaces for some reason).

Hi GOG,

pls. avoid blanks (and $, |, &) in Linux filenames, as is the case in your scripts, e.g. 'GOG Games'. They cause a lot of problems, result in errors, paths can not be found, etc. because a blank wasn't escaped or quoted correctly or the escape got lost when passed along to a new shell.

On the command line blanks are meant to be delimiters, in strings they must be escaped, in shell-scripts they are the cause that files and paths can not be found if not escaped correctly, taking into account that escaping get's lost when passed along.

Use underscores instead, e.g. 'GOG_Games', it'll make a lot of lives easier, and a lot of answers to questions like "Why does my dlc to game xyz not find the game directory ?' obsolete ;-)

Cheers, and happy playing

Reminds mes of an issue I have with soundtracks; for whatever reason, soundtracks insist on putting multiple spaces in every single filename. Makes it more of a pain than it should be to, say, write a script to convert a bunch of them from one format to another.

To be fair, things like a dir full of spaced flac files is far easier to deal with than say spaces in scripts or worse in game code.
In the first case you can just use ' ' but in the latter it gets awfully inconvenient at times.

I hope you do have winetricks, and I cant vouch for any Debian-originated package modifications that could affect performance but using wine-staging is generally better in many cases.

reference
https://infotainmentbeats.com/

By the way, I've been having a performance issue when playing Stranger of Sword City Revisited under WINE (current debian testing version, with dxvk). Any idea of why this would be happening, and if there's any tweaks that can speed performance significantly for modern, but not especially demanding, games?

(Note that this performance issue only affects dungeon exploration, not combat or town.)

I'm sorry but should I know what your cryptic raw quote of one of my rather old posts, and without any of your commentary, means?

I don't think it's even remotely close to be possible to help you with this amount of info provided.